SW. Sci. Med. Vol. 30, NO. 7. pp. 829-835, 1990 Printed in Great Bntain. All rights resewed
0277-9536;90 53.00 + 0.00 Copyright C 1990 Pergamon Press plc
THE FRENCH VERSION OF THE NOTTINGHAM HEALTH PROFILE. A COMPARISON OF ITEMS WEIGHTS WITH THOSE OF THE SOURCE VERSION D. BUCQUET, S. CONDONand K. RITCHIE Epidemiologie du Vieillissement et de L’Incapacite, INSERM CJF 88-12, Chr La ColombikePavilion 52, 555, Route de Ganges, F-34059 Montpellier Cedex, France Abstract-The efficient and reliable assessment of general community health requires the development of comprehensive and parsimonious measures of proven validity. The Nottingham Health Profile (NHP) has been demonstrated to be a reliable indicator of common expressions of discomfort and stress in the general population. The present paper describes its linguistic adaptation into French, the derivation of item weights by Thurstone’s method of paired comparisons and the comparison of item weights across various sociodemographic groups. There is more similarity than variation on the valuation of the state of health explored by the NHP between the French and the British population as little inter-cultural or inter-linguistic variations were found. The differences in judgement of severity elicited across sociodemographic groups in the French sample cast some doubts on the relevance of general weights for use in population surveys. Key words-Nottingham comparisons, validation
Health Profile, weighting self-reported
INTRODUCTION Development work on instruments contributing to the assessment of health status via general population surveys is an important contemporary public health research axis. Within INSERM (Institut National de la SantC et de la Recherche MMicale) the need to find accurate and reliable indicators on which to base the planning, provision and evaluation of health services has stimulated research on health measures and reactivated research into perceived health measures. After the development of morbidity indicators and indicators of consequences of chronic illness, it was felt that an indicator of subjective health was needed. The possibility of creating a French instrument was considered at an early stage, although the Nottingham Health Profile (NHP) was a strong candidate for adaptation into French. Evidence of successful validation tests was published and evidence of its potential contribution to health status population surveys in conjunction with other measures such as incapacity or medico-social services uptake was demonstrated using community survey data in London [I]. Eventually the decision was taken to adapt the NHP with a view to European homogeneity as other national versions of the NHP were in preparation (Swedish, Spanish, Italian). The research programme on the adaptation of the NHP into French aimed to establish its applicability (portability) in the French context. The objective was to assess whether different cultural and linguistic groups have a common conception of good health, and if not, how the different conceptions may be interpreted, in keeping with the issue raised by the work of Patrick er al. [2]. The main steps consisted of the production of the French version and the generation of French item weights. The present article
morbidity statements, cross-cultural
displays comparisons of French and British item weights and examines the contribution of sociodemographic characteristics in the determination of weights in the French sample. METHOD Description of the Nottingham Health Profile
The NHP is a questionnaire designed to measure social and personal effects of illness, to capture self-reported morbidity. It consists of two parts. Part I of the Nottingham Health Profile contains 38 subjective statements, drawn from a pool of over 2000 commonly-used expressions of health problems, gathered from members of the public [3, pp. g6-g7]. These statements form six sections relating to the following areas: sleep, energy, pain, physical mobility, social isolation and emotional reactions. The number of statements in each section varies, from three in the energy section to nine in the emotional reactions section. Within each section an aggregation of responses is made possible by the use of items weights determined on general population sample using Thurstone method of paired comparisons. Part I only was selected for adaptation into French. Part II consists of six very general statements which were not taken into consideration in this programme. Production of the French version The production of the French version (Indicateur de SantC Perceptuelle de Nottingham = ISPN) involved rigorous translation, back translation and linguistic validation. This was felt essential in such a cross-cultural adaptation as conceptual as well as semantic equivalents had to be found in the second language [3, pp. 203-209; 41. A bilingual research 829
830
D. BIXQUET et al.
team was involved in the adaptation project, including individuals familiar with both cultures [5, pp. 13-181 as recommended by Deutcher [6]. The production of the French version observed the syntactical constraints specified in the methodology used by the Nottingham team. These constraints include the use of short sentences, the avoidance of negative forms (to reduce response ambiguity), exclusion of metaphors, subjunctives or other sophisticated constructions thus avoiding the ‘posh effect’. Commonly-used and easily-understood French sentences were selected, reflecting as closely as possible the notions contained in the original instrument. The ISPN is enclosed. Comparisons of French and British items weights and contribution of sociodemographic characteristics in the determination of weights in the French sample
This section gives a brief account of the methodology used to generate the item weights for the ISPN. A quota method was used to select a population sample stratified according to sex, age and patient (hospital out-patients) or non-patient status. Information relating to profession and whether in paid employment was also collected. Six-hundred and twenty-five persons were interviewed, with both sexes represented almost equally (306 men and 319 women). This population of ‘judges’ was sought in similar ‘recruitment centres’ to those used in the production of the British weights [7] and for the Swedish version [8]. There were slightly more patients than non-patients interviewed (I 76 male patients and 179 female patients, 130 male non-patients and 140 female non-patients). The population was divided into three age groups: 18-39 (169), 40-64 (224) and 65 and over (132). Seven interviews, which were considered to be invalid because of interruptions during the interview or inappropriate attitude of the subject, were excluded. A wide distribution of social backgrounds was sought through the selection of a variety of recruitment centres. The non-patient population was found among employees at a rehabilitation clinic, administrative staff and research workers at INSERM, workers at a waste disposal firm, workers and employees in three departments of the Assistance Publique de Paris (garages, warehouses and laundries), young women consulting at a family planning clinic and persons accompanying out-patients at the ‘patient* recruitment centres. The patient population consisted of out-patients consulting doctors at a teaching hospital and at a geriatric hospital Due to problems of access to appropriate recruitment centres, only half of the expected number of elderly persons were interviewed. Interviewers were given a half-day briefing and equipped with a quota sheet for each questionnaire section. *Potential users of the ISPN and its weights are strongly advised to apply to the authors for permission before considering applying the ISPN in any survey. Several ‘standards of good practice’ were issued in [S], one of which makes obligation to potential users to return a minimal data set to contribute to a centralized NHP data base.
The method used to calculate item weights was Thurstone’s Paired Comparisons [9], following the procedure outlined by McKenna et al. [7] in order to replicate as strictly as possible the initial procedures established by the Nottingham team. This standardization requirement has also been observed by both the European and Swedish teams [8] in their adaptation of the NHP. According to this procedure, each item is paired with each of the others in the same section and the groups of pairs are presented for judgement, or perception of relative severity, to a population sample. The observed frequencies of relative severity are ultimately transformed into weights totalling a hundred per section. The sequence of the pairs of statements was selected using random number tables. In addition, the positioning of each statement on the card was randomized (left or right). The order of presentation of the cards was reversed for half the population sample. Each ISPN section was dealt with separately and put to the same number of judges in each subsample. The ‘energy’ section was put to the same subjects as those judging the ‘sleep’ section statements, since the former contained only three pairs of statements. Comparison
of the French and British
weights.
Non-parametric statistics were used to compare the French and the British weights. Spearman’s rank correlation coefficient was calculated on the French and British ranks for each section. Analysis of weights across sociodemographic groups within the French sample. Cross-tabulations of per-
ceived severity for each pair of items within each dimension by sociodemographic variables were performed. Significant associations were identified by Chi-squared tests at the 5% significance level. As an example, weights for the physical mobility section were calculated by socioeconomic groups (SEG) and compared in the first instance to the previously obtained weights on the whole population sample. In a second step weights obtained for each SEG were compared to weights obtained for other SEG (SEGl/SEGZ, SEG3, SEGQ SEGZ/SEG3, SEG4; SEG3/SEG4; see legend in Table 3) using Spearman’s rank correlation coefficient. This was carried out as an exercise, bearing in mind that with 125 subjects the possible variations recorded with the cross-tabulations might not be discernable in the weights. RESULTS AND Comparison
DISCLJSSlON
of the French and British weights
Results are presented in Table l*. Whilst no significant difference was found between rankings for the energy, social isolation, physical mobility and sleep sections, marked discrepancies were noted for the pain and the emotional reactions sections: Spearman’s r = 0.762 and 0.583. The closeness of the items weights for the two ideas “I can only walk about indoors” and “I need help to walk about outside” suggests a difficulty on the part of french judges to distinguish these notions (mobility section). Whereas the former is attributed second rank by the French, it is in fourth rank for the English. Since the conceptual equivalence of the source and translated statements is agreed and there
831
The French version of the NHP Table
I. Comparison
of the French
and English
Statements PHYSICAL mcapoble
I
pour
marcher
des d$icultbs
d m’habilier
oks d@cultis
I have troubles J’oi
ci rester
getting
du ma/ d mower
longtemps
I
des di@wltt+
up and down stairs or steps ou b descendre
/es escoliers
d me pencher
du ma1 d tendre
Spearman’s
le bras (pour
ottroper
rank order correlation
I feel I am a burden I
l’impression
Il.54
2
13.71
12.69
3
12.02
12.61
4
II.46
II.20
5
11.44
10.79
6
9.69
10.57
7
8.51
9.30
8
les objets)
coefficient
we
charge pour
P -co.01
r = 0.929
ISOLATION
to people
d’itre
13.82
en ovont
SOCIAL J’oi
I
ou les marches
find it hard to reach for things
J’ai
21.30
debout
I find it hard to bend J’oi
19.28
English rank
ou ci me dkshobiller
find it hard IO stand for long
J’oi
French rank
dehors
find it hard IO dress myself
J’ai I
besoin &aide
English weight
de marcher
I can only walk about indoors Pour marcher, je suis limitP d I’intlrieur I need help to walk about outside J’oi
French weight MOBILITY
I’m unable to walk at all Je suis rorolement
weights
24.59
22.53
1
I
20.43
22.01
2
2
20.03
20.13
3
3
18.59
19.36
4
4
16.36
15.97
5
5
15.49
16.21
I
13.24
9.3
I
2
12.42
13.99
3
12.13
10.47
4
10.83
12.01
5
10.55
13.95
6
8.91
7.08
7
8.87
7.22
8
1.58
9.76
9
les atttres
feel lonely
Je me seas seul I
feel there is nobody
J’ai
I’impression
I’m finding
I am close to
de n’oooir
personae
de proche
it hard to make contact
J’oi
des diflcultks
I’m
finding
J’ai
des dificultis
d entrer
ti qui parler
with people
en contact
aoec les mares
it hard to get on with people
Spearman’s
d m’entendre
otec
rank order correlation
les autres
coefficient
r=l
EMOTIONAL
REACTIONS
I feel that life is not worth living Je trove
que la uie tte taut
I’ve forgotten
per
la peine d’itre
what it’s like to enjoy myself
Je me rends compte que plus rien ne me fait I
&cue
ploisir
feel as if I’m losing control
J’oi
du mal ci faire
Things
face
are getting
oux iv&tements
me down
Je suis de plus en plus dhcouragt! I
wake up feeling depressed
Je me rtkeille Worry J*ai
dkprimt
is keeping
le main
me awake at night
des soucis qui m’empkhent
de dormir
The days seem to drag Je trouve
les journC;es interminobles
I’m feeling on edge Je me sens nerceux,
tendu
I lose my temper easily these days Je me mets focilement
Spearman’s
en coke
ces temps-ci
rank order correlation
coefficient
NS
r = 0.583
PAIN I’m in constant J’ai 1
pain
des douleurs
have unbearable
J’oi
pain
des douleurs des douleurs
I
walk
I’m
in pain when going up/down des douleurs
en montont
stairs or steps
ou en descendant
Ies escaliers
I
19.74
2
12.73
12.91
3
II.40
Il.22
4
des douleurs
find it painful des douleurs
10.44
5.83
5
10.36
8.96
6
9.69
9.99
7
9.58
10.49
ou Ies marches
I’m in pain when I’m standing
J’ai
17.66
quand je morche
J’ai J’oi
I
la twit
I’m in pain when Je souS;e
20.86
insupportables
I have pain at night I’ai
18.14
en permanence
quand je suis &bout
to change
position
quand je change de position
I’m in pain when I’m sitting
8
Je souflre quand je suis oasis
Spearman’s
rank order correlation
r = 0.762
coefficient
P < 0.05
SLEEP I take tablets to help me sleep Je prends
des midicaments
pour
I lie awake most of the night
26.33
22.37
1
2
22.86
27.26
2
I
dormir
(Table
I continued
owrlettf
832
D.
Table
BUCQUET
I
resre CwiliP
sleepbadly
une grande
mol la nuit
II takes
me a long
mm beaucoup
I’m
waking
partie
time
to get IO sleep hours
trPs tBt le matin
Spearman’s
rank
English
French
English
weight
weight
rank
rank
20.36
21.70
3
3
16.50
16.10
4
4
13.94
12.57
5
5
de temps ci m’cndormir
up in the early
Je me r&ilk
French
de la twit
at night
Je don Je
al.
I-continued]
statements Ie
er
order
of the morning
et j’oi
correlation
du ma/ ci me rendormir I = 0.9
coefficient
P < 0.01
ENERGY I’m
tired
all the time
39.00
39.20
I
I
34.48
36.80
2
2
26.54
24.00
3
3
Je me sens tout le temps /higut! Everything Tout
is an effort
me demande
I soon
run out
Je me Jarigue Spearman’s
un eflort
of energy cite
rank
order
correlation
co-efficient
is no clear reason why there should be a cross-cultural difference, this must be the result of other factors. Moreover, the weights for the statements ranked 2 to 6 in both languages are at short distances from one another. For the sleep section, the weights and ranks are very similar. There is one major difference: there is a similar distance between the first and second ranks for both populations; but the French have judged taking tablets at night as more serioius than lying awake at night. Does this suggest a ‘cross-national variation’? Or that the taking of tablets is not on a continuum along with the other items? For the pain section, more differences were found. This is not surprising as cultural discrepancies in the reporting of pain have been documented since Zborowski in 1952 [IO]. In the present study, these differences relate to the lower four ranks. The most striking difference is that the French have ranked “having difficulty going up and down stairs or steps” fifth in the hierarchy whilst this statement was attributed eighth rank in the English sample. Similarly, the French ranked “having pain when sitting” eighth and for the English it was fifth. For the latter case, it is difficult to see a reason; moreover, the two versions have similar weights. However, for the item concerning stairs the difference in weight is considerable: this could be due to an environmental or habitat factor. Does this French population use stairs more often, e.g. access to apartments, stairs in underground stations? For the emotional reactions section, there are three important discrepancies. Firstly, the statement “I’ve forgotten what it’s like to enjoy myself”. This has rank seven for the English and rank two for the French. The authors suspect that this is not due to cross-national variation, but rather a sign of linguistic distance between the source and translated versions. The selected expression in the French version is regarded as very serious, whilst the English statement is a cliche. Secondly, the statement “Worry is keeping me awake at night” appears to be more serious to the English than to the French. Are worries more ‘normal’ for the Parisian population interviewed? Similarly, the English considered the statement “I lose my temper easily these days” to be more serious than did the French. Here again, this could be a difference stemming from the nature of the population sample
r=l
rather than being a ‘cross-national’ difference. Another statement worth mentioning is “the days seem to drag”. In English, this is a commonly-used phrase whereas in French it does not have such an immediate meaning and is somewhat artificial. The result probably reflects this difference in impact. It is interesting to note one last point concerning the French version of the statement “I feel as if I’m losing control”. Since the philosophy of the original instrument was that it should contain statements used by people to express states of health, a semantically closer translation was not satisfactory (“perdre controle de soi”) because this expression is not in common use. Thus a commonly-used statement which expresses as closely as possible the degree of distress was chosen: “j’ai du ma1 a faire face aux evtnements”. Differences may exist between the French and the British sample with regard to such factors as habitat, family situation, educational background, employment conditions, age structure. Such variables have been shown to be relevant in recognizing the variations in perception of health [I l-131. In their comparison of health status values, Patrick et al. stressed that “The professional group and precise context in which judgments are obtained may well influence scale values and these factors should be studied systematically under controlled conditions before concluding that professionals and consumers differ in their judgments” [2]. Unfortunately, for the present comparison study, no details were available to us on the English sample, since no population quota was reported for the British study. Hunt et al. argued, whilst reporting their experience in national adaptations of the NHP in Arabic, American English and Spanish American, that “problems of literal translation or of functional equivalency aside, socio-emotional items are likely to cause the most trouble and items relating to more universal experiences, the least” [3, p. 2161. In the French adaptation, whilst this was true for the emotional reactions section, there was little difficulty in finding equivalents for the social isolation items. The comparison of French and British weights described has been unable to explain some of the observed discrepancies and suggests the need for an alternative research design. Nonetheless, the French
The French
version
of the NHP
833
Table 2. Number of discordant oairs bv section and sociodemoaraohic
R~OUD
(at the 5% level)
Number of discordant pairs Section (No. of items)
Age
Sex
SEG
Econ. active
Whether patient
Emotional reactions (9)
3
I
Pain (8) Physical mobility (8) Social isolation (5) Energy (3) Sleep (5) Column totals (38)
0 0
0 2
I 3 4
0 2 4 0 0
I
0
0
0
0
0
6 0 2 I 0
I
0
0
0
0
5
3
8
9
6
Total discordant pairs
Total pairs by section
Number of
II 5 I2 2 0 I 31
36 28 28 IO 3 IO 115
123 124 130 124 124. 124’ 625 Subjects interviewed
subjects
Total pairs by sewon: arrangement of 3” items by 2. Number of discordant pairs: number of pairs of items in a section for uhich exists a statistically significant difference by Age, Sex at the 5% level. *The same subjects were asked to express their judgement for these two sections due to the small number of pairs.
weights obtained do indicate that the ISPN is an instrument likely to detect a similar level of distress to the NHP. There is far more similarity than variation on the valuation of the state of health explored by the NHP between the French and British populations. There is little inter-cultural or inter-linguistic variation. There results somehow confirm the decision to adapt an existing instrument rather than to create one ex nihilo. Analysis of weights across different sociodemographic groups within the French population sample
The variation of item weights by age, sex, SEG, employment and patient status was determined in order to further assess the portability of the instrument. This procedure was conducted to estimate inter-group variations in judgements of items severity
within the French sample, although none have been reported in either the English or the Swedish samples. It is worth indicating at this point that the French items were demonstrated elsewhere to be stable over time [5, pp. 42431. Using the chi-square test with 5% level of significance, the judgements for 31 of the total 115 pairs were found to be discordant (Table 2). For example, for the physical mobility section, the frequency of item 2 (I find it hard to bend) being judged more severe than item 4 (I find it hard to stand for long) was statistically lower among men (3 1%) than among women (56%). The frequency of item 4 being judged more severe than item 6 (I find it hard to dress myself) was statistically higher among men (56%) than among women (36%). Other significant differences were found for this very dimension according
Table 3. Differences in judgement for section physical mobility by sociodemographic variables (N = 124) Variables
Pairs
Judgements (%) Male
Female
P
2 > 4’ 4~6
31.25 56.25
56.06 36.36
0.004 0.023
1
2
224 3>7 5>6 2>6
26.09 8.57 69.57 34.78
57.14 37.14 57.14 21.43
Yes
No
P
2>3 1>3
39.74 42.31
21.15 25.00
0.026 0.043
Yes
No
P
7>8 I>6 3>5 5>6 I>7
25.35 21.13 43.66 52.11 19.72
IO.17 40.68 27.12 69.49 37.29
0.026 0.039 0.050 0.044 0.026
Sex
SEGt
Whether economically active
Whether oatient
3 58.06 22.86 41.94 35.48
4
P
26.92 31.43 76.92 69.23
0.014 0.041 0.040 0.003
l2 > 4 = Statement 2 judged more severe than statement 4. I = I find it hard to reach for things. 2 = I find it hard to bend. 3 = I have troubles getting up and down stairs or steps. 4 = I find it hard to stand for long. 5 = I can only walk about indoors. 6 = I find it hard to dress myself. 7 = I need help to walk about outside. 8 = I am unable to walk at all. tSEG 14 regroup INSEE categories: SEG I = self-employed craftsmen, shop-keepers and company managers, senior executives, intellectual and liberal. SEG 2 = middle executives and occupations. SEG 3 = employee and service workers. SEG 4 = skilled, semi-skilled and unskilled workers.
D. BUCQIJET er al.
834
Table 4. Weights for the physical mobility section by SEG SEG
Statements in the physical mobilitysection 5 6 7 2 3 4
I 6.60 9.09 8.48 9.05 a.51
I
2 3 4 All SEG
8.46 9.30 9.88 II.13 9.69
a.92 il.38 11.12 12.40 II.44
to SEG, whether economically active and whether patient or non-patient (Table 3). Variations were found for all dimensions with the five sociodemographic variables mentioned above. The physical mobility section stands out as the section in which most discordances occur proportionately. When moving from cross-tabulations to the calculations of weights and comparing the weights obtained for each SEG in the physical mobility section, the weights obtained for SEG4 are statistically different only from those obtained for SEG2 and SEG3 (Tables 4 and 5). The question of the selection of an appropriate level of significance to elicit acceptable differences, especially in the domain of perceived health should be addressed at this point. Rosser and Kind have argued that “In any analysis which involves repeated testing of new data there must be some degree of caution about the extent to which any significant difference may have occurred by chance” and said that “If we place confidence in all the significant findings at the 5% level, we may underestimate the extent to which there is social consensus’* [14]. Here, significant differences were found for 31 of the 115 pairs at the 5% level of significance. This level reveals more differences than when the 2% level is used (9 discordant pairs) and fewer than when the 8% level is used (42 discordant pairs). This means that, using a 5% level, a lower level of consensus is found than when using a 2% level, and hence the validity of the weights for the general population is less satisfactory. Owing to this particular field of health perception, and more strongly, to the danger of ‘putting on the market’ an instrument with such an attractive feature as a synthetic figure (a unique score by section), we felt the choice of the 5% level of significance was not unfair to the instrument. If one were to adopt a l/1000 level of significance, no difference would be indicated and one could confidently conclude that there are no variations in state of health valuation by Table 5. Differences in weight for the physical mobility section, Spearman’s rank correlation coefficient Comparison of A/B SEG SEG SEC SEG SEC SEG SEG SEG SEG SEG
I/all SEG Z/all SEG 3/ail SEG 4/ail SEG I/SEG 2 I/SEG 3 I/SEG 4 2/SEG 3 Z/SEG 4 3/SEG 4
Correlation coefficient
D2
0.95 0.95 0.95 0.81 0.83 0.93 0.86 0.93 0.69 0.7 I
4 4 4 I6 I4 6 I2 6 26 24
For alpha = 5% and n = 8: R = 0.74.
9.92 10.59 9.92 13.69 II.46
12.05 13.33 13.52 14.09 13.82
9.19 13.10 13.17 9.30 12.02
14.28 12.84 14.96 13.03 13.71
8 29.98 20.38 18.95 17.32 19.28
age, sex, etc. Such a conclusion, when using the instrument in population surveys, would not be neutral and lead to aggregate in a NHP score a socioeconomic component and a purer distress component which is only what the NHP is supposed to pick up. In fact, it is the question of the p risk (lack of power) which should be addressed here rather than the question of the a risk (risk of error). The question is not so much to reject the null hypothesis (null hypothesis = there is no difference), with a risk of a%, when it is true, than to accept it when it is false with a risk of /?“/o. The elucidation of differences in judgement brings into question the use of Thurstone’s method of paired comparisons for weighting the French items of the ISPN. The underlying assumption is that people are able to express a preference for one health state as opposed to another which may not be appropriate in all cultures. Whether judges, in this case French judges, were able to choose the more serious of two subjective expressions of health problems is a central issue. The reactions of the judges were noted by the interviewers. Some judges found the interviews for the pain, physical mobility and emotional reactions sections too long (28, 28 and 36 pairs respectively). Some judgements evidently were difficult to make, notably in the pain, physical mobility, energy and sleep sections. Also, the notion of a ‘general view’ of the health statements was not grasped easily by ail the judges. These difficulties may have lead subjects to decide at random and this could well be a factor contributing to these inter-group variations. Kind [15] has criticized the use of this method of weighting the NHP on the grounds that (i) judges ratings are possibly inconsistent, (ii) there is a lack of psychological continuum in the sleep section and (iii) there are items with similar scale values. Hunt et al., on the other hand, questioning whether perceptions are indeed logical, make a case for retaining the item referring to sleeping tablets as this is perceived as a health problem and also affects the responses to the other items [3, pp. 92-931. They also point out that, in contrast with classical psychological scaling, when scaling in perceived health two statements describing different problems may be judged to be of similar severity by a patient panel. Kind had also noted that an alternative statistical model produced different weights: however, subsequent examination of this situation led Hunt to conclude that the Thurstone method for weighting perceived health statements was preferable [3, p. 951 as a means of obtaining lay judgements of the comparative severity of subjective statements of health problems. Furthermore, the principle of seeking an evaluation of the relative severity of the items is coherent with the philosophy of the instrument.
The French version of the NHP
835
CONCLUSION
The weighting
study has provided a means of validating the translation of the NHP items into French. The comments made during the course of the interviews neither reflected upon the understanding nor on the familiarity of the expressions, confirming the immediate intelligibility of the French version. It cannot be determined whether the few major differences in rank which were found were a result of ‘cross-cultural’ differences in perception and judgement, were indicative of problems of exact equivalence in translation or were simply the outcome of
random variation in response. Although there is a high level of agreement in the weighting of the NHP items, there is nevertheless a non-negligible contribution of sociodemographic characteristics in the generation of items weights. The present authors warn future users of the ISPN to be wary of the use of weights, as they stand, and to complement their results with other expressions of information contained in the instrument which, indeed, is precious (percentage of items responded positively, per section or on the whole, simple addition of positive responses . . . ). Certainly, the generation of specific weights for each of the vast number of sociodemographic sub-groups in the population is not feasible and, even if possible, would exclude comparability [ 161. Overall, the study suggests that, in this translation and adaptation process, the concern about comparability of items weights between sociodemographic groups, SEG in particular, predominates over the concern about cross-lingual comparability. The results have implications for the projects considering adapting the NHP into other European languages. Further studies on the British and Swedish data sets would shed light on this crucial problem in the future of comparative health measurement at the European scale. These results could also prompt the Spanish team to consider a modified sampling frame to conduct to calculation of Spanish weights. Acknorledgemenrs-The project for the adaptation of the Nottingham Profile into French was financed by the Economic and Social Research Council, the Institut National de la Sante et de la Recherche Medicale (INSERM, Grant No. 86.8.014). the Assistance Publique de Paris and the Mission Recherche Experimentation. The authors are grateful to Sonja Hunt, Sarah Curtis and Alain Colvez for their support and advice.
REFERENCES
1. Bucquet D. and Curtis S. Socio-demographic variation in perceived illness and the use of primary care: the value of community survey data for primary care service planning. Sot. Sci. Med. 23, 734-744, 1986. 2. Patrick D. L. ef al. A cross-cultural comparison of health status values. Am. J. publ. Hlfh 75, 1402-1407, 1985. 3. Hunt S. M., McEwen J. and McKenna S. P. Measuring Health S~ofus. Croom Helm, Kent, 1986.
4. Hantrais L. and Ager D. The language barrier to effective cross-national research. Cross-National Research Papers, Vol. 1. Aston Modem Lang. Club. Aston Univ., pp. 2940, 1985. 5. Bucquet‘D. and Condon S. Adaptation into French of the Nottinnham Health Profile and Operational Characteristics of-the French Version. May ‘1988. INSERM U 164, F-94807 Villejuif Cedex, 1988. 6. Deutscher I. Asking questions cross-culturally: some problems of linguistic comparability. In Compararire Research Methods (Edited by Warwick D. P. and Osherson S.), pp. 163-186. Prentice Hall, New Jersey, 1973. 7. McKenna S. P., Hunt S. M. and McEwen J. Weighting the seriousness of perceived health problems using Thurstone’s Method of Paired Comparisons. Im. J. Epiakn. 10, 93-97, 1981. 8. Hunt S. M. and Wilkund I. Cross-cultural variation in the weighting of health statements: a comparison of English and Swedish valuations. Hlrh Poliq 8, 230, 1987.
9. Thurstone Psycho/.
L. L. A law of comparative
Reu. 34, 273-286,
judgement.
1927.
10. Zborowski M. Cultural components in response to pain. J. Sot. Issues 8, 16-24,
1952.
Il. D’Houtaud A. and Field M. G. The image of health: variations in perception by social class in a French noeulation. Social. Hlth Illness 6. 30-58. 1984.
- .
12. Fillenbaum G. G. Social context and self-assessments of health among the elderly. J. Hlrh sot. Behau. 20,45-5 I, 1979.
13. Ekerdt D. J. and Bosse R. Change in self-reported health with retirement. Inr. J. Aging Human Der. 15, 213-223, 1982. 14. Rosser R. and Kind R. A scale of valuations of states of illness: is there a social consensus? Int. J. Epidem. 7, 357, 1978.
15. Kind P. A comparison of two models for scaling health indicators. Inl. J. Epidem. 11, 271-275, 1982. 16. Colvez A., Gardent H. and Bucquet D. Validation d’indicateurs en gerontologie. Application au domaine des indicateurs de capacitt fonctionnelle. E&IS C.T.N.E.R.H.I., Paris, 1989. In press.
0277-9536;90 53.00 + 0.00 Copyright C 1990 Pergamon Press plc
THE FRENCH VERSION OF THE NOTTINGHAM HEALTH PROFILE. A COMPARISON OF ITEMS WEIGHTS WITH THOSE OF THE SOURCE VERSION D. BUCQUET, S. CONDONand K. RITCHIE Epidemiologie du Vieillissement et de L’Incapacite, INSERM CJF 88-12, Chr La ColombikePavilion 52, 555, Route de Ganges, F-34059 Montpellier Cedex, France Abstract-The efficient and reliable assessment of general community health requires the development of comprehensive and parsimonious measures of proven validity. The Nottingham Health Profile (NHP) has been demonstrated to be a reliable indicator of common expressions of discomfort and stress in the general population. The present paper describes its linguistic adaptation into French, the derivation of item weights by Thurstone’s method of paired comparisons and the comparison of item weights across various sociodemographic groups. There is more similarity than variation on the valuation of the state of health explored by the NHP between the French and the British population as little inter-cultural or inter-linguistic variations were found. The differences in judgement of severity elicited across sociodemographic groups in the French sample cast some doubts on the relevance of general weights for use in population surveys. Key words-Nottingham comparisons, validation
Health Profile, weighting self-reported
INTRODUCTION Development work on instruments contributing to the assessment of health status via general population surveys is an important contemporary public health research axis. Within INSERM (Institut National de la SantC et de la Recherche MMicale) the need to find accurate and reliable indicators on which to base the planning, provision and evaluation of health services has stimulated research on health measures and reactivated research into perceived health measures. After the development of morbidity indicators and indicators of consequences of chronic illness, it was felt that an indicator of subjective health was needed. The possibility of creating a French instrument was considered at an early stage, although the Nottingham Health Profile (NHP) was a strong candidate for adaptation into French. Evidence of successful validation tests was published and evidence of its potential contribution to health status population surveys in conjunction with other measures such as incapacity or medico-social services uptake was demonstrated using community survey data in London [I]. Eventually the decision was taken to adapt the NHP with a view to European homogeneity as other national versions of the NHP were in preparation (Swedish, Spanish, Italian). The research programme on the adaptation of the NHP into French aimed to establish its applicability (portability) in the French context. The objective was to assess whether different cultural and linguistic groups have a common conception of good health, and if not, how the different conceptions may be interpreted, in keeping with the issue raised by the work of Patrick er al. [2]. The main steps consisted of the production of the French version and the generation of French item weights. The present article
morbidity statements, cross-cultural
displays comparisons of French and British item weights and examines the contribution of sociodemographic characteristics in the determination of weights in the French sample. METHOD Description of the Nottingham Health Profile
The NHP is a questionnaire designed to measure social and personal effects of illness, to capture self-reported morbidity. It consists of two parts. Part I of the Nottingham Health Profile contains 38 subjective statements, drawn from a pool of over 2000 commonly-used expressions of health problems, gathered from members of the public [3, pp. g6-g7]. These statements form six sections relating to the following areas: sleep, energy, pain, physical mobility, social isolation and emotional reactions. The number of statements in each section varies, from three in the energy section to nine in the emotional reactions section. Within each section an aggregation of responses is made possible by the use of items weights determined on general population sample using Thurstone method of paired comparisons. Part I only was selected for adaptation into French. Part II consists of six very general statements which were not taken into consideration in this programme. Production of the French version The production of the French version (Indicateur de SantC Perceptuelle de Nottingham = ISPN) involved rigorous translation, back translation and linguistic validation. This was felt essential in such a cross-cultural adaptation as conceptual as well as semantic equivalents had to be found in the second language [3, pp. 203-209; 41. A bilingual research 829
830
D. BIXQUET et al.
team was involved in the adaptation project, including individuals familiar with both cultures [5, pp. 13-181 as recommended by Deutcher [6]. The production of the French version observed the syntactical constraints specified in the methodology used by the Nottingham team. These constraints include the use of short sentences, the avoidance of negative forms (to reduce response ambiguity), exclusion of metaphors, subjunctives or other sophisticated constructions thus avoiding the ‘posh effect’. Commonly-used and easily-understood French sentences were selected, reflecting as closely as possible the notions contained in the original instrument. The ISPN is enclosed. Comparisons of French and British items weights and contribution of sociodemographic characteristics in the determination of weights in the French sample
This section gives a brief account of the methodology used to generate the item weights for the ISPN. A quota method was used to select a population sample stratified according to sex, age and patient (hospital out-patients) or non-patient status. Information relating to profession and whether in paid employment was also collected. Six-hundred and twenty-five persons were interviewed, with both sexes represented almost equally (306 men and 319 women). This population of ‘judges’ was sought in similar ‘recruitment centres’ to those used in the production of the British weights [7] and for the Swedish version [8]. There were slightly more patients than non-patients interviewed (I 76 male patients and 179 female patients, 130 male non-patients and 140 female non-patients). The population was divided into three age groups: 18-39 (169), 40-64 (224) and 65 and over (132). Seven interviews, which were considered to be invalid because of interruptions during the interview or inappropriate attitude of the subject, were excluded. A wide distribution of social backgrounds was sought through the selection of a variety of recruitment centres. The non-patient population was found among employees at a rehabilitation clinic, administrative staff and research workers at INSERM, workers at a waste disposal firm, workers and employees in three departments of the Assistance Publique de Paris (garages, warehouses and laundries), young women consulting at a family planning clinic and persons accompanying out-patients at the ‘patient* recruitment centres. The patient population consisted of out-patients consulting doctors at a teaching hospital and at a geriatric hospital Due to problems of access to appropriate recruitment centres, only half of the expected number of elderly persons were interviewed. Interviewers were given a half-day briefing and equipped with a quota sheet for each questionnaire section. *Potential users of the ISPN and its weights are strongly advised to apply to the authors for permission before considering applying the ISPN in any survey. Several ‘standards of good practice’ were issued in [S], one of which makes obligation to potential users to return a minimal data set to contribute to a centralized NHP data base.
The method used to calculate item weights was Thurstone’s Paired Comparisons [9], following the procedure outlined by McKenna et al. [7] in order to replicate as strictly as possible the initial procedures established by the Nottingham team. This standardization requirement has also been observed by both the European and Swedish teams [8] in their adaptation of the NHP. According to this procedure, each item is paired with each of the others in the same section and the groups of pairs are presented for judgement, or perception of relative severity, to a population sample. The observed frequencies of relative severity are ultimately transformed into weights totalling a hundred per section. The sequence of the pairs of statements was selected using random number tables. In addition, the positioning of each statement on the card was randomized (left or right). The order of presentation of the cards was reversed for half the population sample. Each ISPN section was dealt with separately and put to the same number of judges in each subsample. The ‘energy’ section was put to the same subjects as those judging the ‘sleep’ section statements, since the former contained only three pairs of statements. Comparison
of the French and British
weights.
Non-parametric statistics were used to compare the French and the British weights. Spearman’s rank correlation coefficient was calculated on the French and British ranks for each section. Analysis of weights across sociodemographic groups within the French sample. Cross-tabulations of per-
ceived severity for each pair of items within each dimension by sociodemographic variables were performed. Significant associations were identified by Chi-squared tests at the 5% significance level. As an example, weights for the physical mobility section were calculated by socioeconomic groups (SEG) and compared in the first instance to the previously obtained weights on the whole population sample. In a second step weights obtained for each SEG were compared to weights obtained for other SEG (SEGl/SEGZ, SEG3, SEGQ SEGZ/SEG3, SEG4; SEG3/SEG4; see legend in Table 3) using Spearman’s rank correlation coefficient. This was carried out as an exercise, bearing in mind that with 125 subjects the possible variations recorded with the cross-tabulations might not be discernable in the weights. RESULTS AND Comparison
DISCLJSSlON
of the French and British weights
Results are presented in Table l*. Whilst no significant difference was found between rankings for the energy, social isolation, physical mobility and sleep sections, marked discrepancies were noted for the pain and the emotional reactions sections: Spearman’s r = 0.762 and 0.583. The closeness of the items weights for the two ideas “I can only walk about indoors” and “I need help to walk about outside” suggests a difficulty on the part of french judges to distinguish these notions (mobility section). Whereas the former is attributed second rank by the French, it is in fourth rank for the English. Since the conceptual equivalence of the source and translated statements is agreed and there
831
The French version of the NHP Table
I. Comparison
of the French
and English
Statements PHYSICAL mcapoble
I
pour
marcher
des d$icultbs
d m’habilier
oks d@cultis
I have troubles J’oi
ci rester
getting
du ma/ d mower
longtemps
I
des di@wltt+
up and down stairs or steps ou b descendre
/es escoliers
d me pencher
du ma1 d tendre
Spearman’s
le bras (pour
ottroper
rank order correlation
I feel I am a burden I
l’impression
Il.54
2
13.71
12.69
3
12.02
12.61
4
II.46
II.20
5
11.44
10.79
6
9.69
10.57
7
8.51
9.30
8
les objets)
coefficient
we
charge pour
P -co.01
r = 0.929
ISOLATION
to people
d’itre
13.82
en ovont
SOCIAL J’oi
I
ou les marches
find it hard to reach for things
J’ai
21.30
debout
I find it hard to bend J’oi
19.28
English rank
ou ci me dkshobiller
find it hard IO stand for long
J’oi
French rank
dehors
find it hard IO dress myself
J’ai I
besoin &aide
English weight
de marcher
I can only walk about indoors Pour marcher, je suis limitP d I’intlrieur I need help to walk about outside J’oi
French weight MOBILITY
I’m unable to walk at all Je suis rorolement
weights
24.59
22.53
1
I
20.43
22.01
2
2
20.03
20.13
3
3
18.59
19.36
4
4
16.36
15.97
5
5
15.49
16.21
I
13.24
9.3
I
2
12.42
13.99
3
12.13
10.47
4
10.83
12.01
5
10.55
13.95
6
8.91
7.08
7
8.87
7.22
8
1.58
9.76
9
les atttres
feel lonely
Je me seas seul I
feel there is nobody
J’ai
I’impression
I’m finding
I am close to
de n’oooir
personae
de proche
it hard to make contact
J’oi
des diflcultks
I’m
finding
J’ai
des dificultis
d entrer
ti qui parler
with people
en contact
aoec les mares
it hard to get on with people
Spearman’s
d m’entendre
otec
rank order correlation
les autres
coefficient
r=l
EMOTIONAL
REACTIONS
I feel that life is not worth living Je trove
que la uie tte taut
I’ve forgotten
per
la peine d’itre
what it’s like to enjoy myself
Je me rends compte que plus rien ne me fait I
&cue
ploisir
feel as if I’m losing control
J’oi
du mal ci faire
Things
face
are getting
oux iv&tements
me down
Je suis de plus en plus dhcouragt! I
wake up feeling depressed
Je me rtkeille Worry J*ai
dkprimt
is keeping
le main
me awake at night
des soucis qui m’empkhent
de dormir
The days seem to drag Je trouve
les journC;es interminobles
I’m feeling on edge Je me sens nerceux,
tendu
I lose my temper easily these days Je me mets focilement
Spearman’s
en coke
ces temps-ci
rank order correlation
coefficient
NS
r = 0.583
PAIN I’m in constant J’ai 1
pain
des douleurs
have unbearable
J’oi
pain
des douleurs des douleurs
I
walk
I’m
in pain when going up/down des douleurs
en montont
stairs or steps
ou en descendant
Ies escaliers
I
19.74
2
12.73
12.91
3
II.40
Il.22
4
des douleurs
find it painful des douleurs
10.44
5.83
5
10.36
8.96
6
9.69
9.99
7
9.58
10.49
ou Ies marches
I’m in pain when I’m standing
J’ai
17.66
quand je morche
J’ai J’oi
I
la twit
I’m in pain when Je souS;e
20.86
insupportables
I have pain at night I’ai
18.14
en permanence
quand je suis &bout
to change
position
quand je change de position
I’m in pain when I’m sitting
8
Je souflre quand je suis oasis
Spearman’s
rank order correlation
r = 0.762
coefficient
P < 0.05
SLEEP I take tablets to help me sleep Je prends
des midicaments
pour
I lie awake most of the night
26.33
22.37
1
2
22.86
27.26
2
I
dormir
(Table
I continued
owrlettf
832
D.
Table
BUCQUET
I
resre CwiliP
sleepbadly
une grande
mol la nuit
II takes
me a long
mm beaucoup
I’m
waking
partie
time
to get IO sleep hours
trPs tBt le matin
Spearman’s
rank
English
French
English
weight
weight
rank
rank
20.36
21.70
3
3
16.50
16.10
4
4
13.94
12.57
5
5
de temps ci m’cndormir
up in the early
Je me r&ilk
French
de la twit
at night
Je don Je
al.
I-continued]
statements Ie
er
order
of the morning
et j’oi
correlation
du ma/ ci me rendormir I = 0.9
coefficient
P < 0.01
ENERGY I’m
tired
all the time
39.00
39.20
I
I
34.48
36.80
2
2
26.54
24.00
3
3
Je me sens tout le temps /higut! Everything Tout
is an effort
me demande
I soon
run out
Je me Jarigue Spearman’s
un eflort
of energy cite
rank
order
correlation
co-efficient
is no clear reason why there should be a cross-cultural difference, this must be the result of other factors. Moreover, the weights for the statements ranked 2 to 6 in both languages are at short distances from one another. For the sleep section, the weights and ranks are very similar. There is one major difference: there is a similar distance between the first and second ranks for both populations; but the French have judged taking tablets at night as more serioius than lying awake at night. Does this suggest a ‘cross-national variation’? Or that the taking of tablets is not on a continuum along with the other items? For the pain section, more differences were found. This is not surprising as cultural discrepancies in the reporting of pain have been documented since Zborowski in 1952 [IO]. In the present study, these differences relate to the lower four ranks. The most striking difference is that the French have ranked “having difficulty going up and down stairs or steps” fifth in the hierarchy whilst this statement was attributed eighth rank in the English sample. Similarly, the French ranked “having pain when sitting” eighth and for the English it was fifth. For the latter case, it is difficult to see a reason; moreover, the two versions have similar weights. However, for the item concerning stairs the difference in weight is considerable: this could be due to an environmental or habitat factor. Does this French population use stairs more often, e.g. access to apartments, stairs in underground stations? For the emotional reactions section, there are three important discrepancies. Firstly, the statement “I’ve forgotten what it’s like to enjoy myself”. This has rank seven for the English and rank two for the French. The authors suspect that this is not due to cross-national variation, but rather a sign of linguistic distance between the source and translated versions. The selected expression in the French version is regarded as very serious, whilst the English statement is a cliche. Secondly, the statement “Worry is keeping me awake at night” appears to be more serious to the English than to the French. Are worries more ‘normal’ for the Parisian population interviewed? Similarly, the English considered the statement “I lose my temper easily these days” to be more serious than did the French. Here again, this could be a difference stemming from the nature of the population sample
r=l
rather than being a ‘cross-national’ difference. Another statement worth mentioning is “the days seem to drag”. In English, this is a commonly-used phrase whereas in French it does not have such an immediate meaning and is somewhat artificial. The result probably reflects this difference in impact. It is interesting to note one last point concerning the French version of the statement “I feel as if I’m losing control”. Since the philosophy of the original instrument was that it should contain statements used by people to express states of health, a semantically closer translation was not satisfactory (“perdre controle de soi”) because this expression is not in common use. Thus a commonly-used statement which expresses as closely as possible the degree of distress was chosen: “j’ai du ma1 a faire face aux evtnements”. Differences may exist between the French and the British sample with regard to such factors as habitat, family situation, educational background, employment conditions, age structure. Such variables have been shown to be relevant in recognizing the variations in perception of health [I l-131. In their comparison of health status values, Patrick et al. stressed that “The professional group and precise context in which judgments are obtained may well influence scale values and these factors should be studied systematically under controlled conditions before concluding that professionals and consumers differ in their judgments” [2]. Unfortunately, for the present comparison study, no details were available to us on the English sample, since no population quota was reported for the British study. Hunt et al. argued, whilst reporting their experience in national adaptations of the NHP in Arabic, American English and Spanish American, that “problems of literal translation or of functional equivalency aside, socio-emotional items are likely to cause the most trouble and items relating to more universal experiences, the least” [3, p. 2161. In the French adaptation, whilst this was true for the emotional reactions section, there was little difficulty in finding equivalents for the social isolation items. The comparison of French and British weights described has been unable to explain some of the observed discrepancies and suggests the need for an alternative research design. Nonetheless, the French
The French
version
of the NHP
833
Table 2. Number of discordant oairs bv section and sociodemoaraohic
R~OUD
(at the 5% level)
Number of discordant pairs Section (No. of items)
Age
Sex
SEG
Econ. active
Whether patient
Emotional reactions (9)
3
I
Pain (8) Physical mobility (8) Social isolation (5) Energy (3) Sleep (5) Column totals (38)
0 0
0 2
I 3 4
0 2 4 0 0
I
0
0
0
0
0
6 0 2 I 0
I
0
0
0
0
5
3
8
9
6
Total discordant pairs
Total pairs by section
Number of
II 5 I2 2 0 I 31
36 28 28 IO 3 IO 115
123 124 130 124 124. 124’ 625 Subjects interviewed
subjects
Total pairs by sewon: arrangement of 3” items by 2. Number of discordant pairs: number of pairs of items in a section for uhich exists a statistically significant difference by Age, Sex at the 5% level. *The same subjects were asked to express their judgement for these two sections due to the small number of pairs.
weights obtained do indicate that the ISPN is an instrument likely to detect a similar level of distress to the NHP. There is far more similarity than variation on the valuation of the state of health explored by the NHP between the French and British populations. There is little inter-cultural or inter-linguistic variation. There results somehow confirm the decision to adapt an existing instrument rather than to create one ex nihilo. Analysis of weights across different sociodemographic groups within the French population sample
The variation of item weights by age, sex, SEG, employment and patient status was determined in order to further assess the portability of the instrument. This procedure was conducted to estimate inter-group variations in judgements of items severity
within the French sample, although none have been reported in either the English or the Swedish samples. It is worth indicating at this point that the French items were demonstrated elsewhere to be stable over time [5, pp. 42431. Using the chi-square test with 5% level of significance, the judgements for 31 of the total 115 pairs were found to be discordant (Table 2). For example, for the physical mobility section, the frequency of item 2 (I find it hard to bend) being judged more severe than item 4 (I find it hard to stand for long) was statistically lower among men (3 1%) than among women (56%). The frequency of item 4 being judged more severe than item 6 (I find it hard to dress myself) was statistically higher among men (56%) than among women (36%). Other significant differences were found for this very dimension according
Table 3. Differences in judgement for section physical mobility by sociodemographic variables (N = 124) Variables
Pairs
Judgements (%) Male
Female
P
2 > 4’ 4~6
31.25 56.25
56.06 36.36
0.004 0.023
1
2
224 3>7 5>6 2>6
26.09 8.57 69.57 34.78
57.14 37.14 57.14 21.43
Yes
No
P
2>3 1>3
39.74 42.31
21.15 25.00
0.026 0.043
Yes
No
P
7>8 I>6 3>5 5>6 I>7
25.35 21.13 43.66 52.11 19.72
IO.17 40.68 27.12 69.49 37.29
0.026 0.039 0.050 0.044 0.026
Sex
SEGt
Whether economically active
Whether oatient
3 58.06 22.86 41.94 35.48
4
P
26.92 31.43 76.92 69.23
0.014 0.041 0.040 0.003
l2 > 4 = Statement 2 judged more severe than statement 4. I = I find it hard to reach for things. 2 = I find it hard to bend. 3 = I have troubles getting up and down stairs or steps. 4 = I find it hard to stand for long. 5 = I can only walk about indoors. 6 = I find it hard to dress myself. 7 = I need help to walk about outside. 8 = I am unable to walk at all. tSEG 14 regroup INSEE categories: SEG I = self-employed craftsmen, shop-keepers and company managers, senior executives, intellectual and liberal. SEG 2 = middle executives and occupations. SEG 3 = employee and service workers. SEG 4 = skilled, semi-skilled and unskilled workers.
D. BUCQIJET er al.
834
Table 4. Weights for the physical mobility section by SEG SEG
Statements in the physical mobilitysection 5 6 7 2 3 4
I 6.60 9.09 8.48 9.05 a.51
I
2 3 4 All SEG
8.46 9.30 9.88 II.13 9.69
a.92 il.38 11.12 12.40 II.44
to SEG, whether economically active and whether patient or non-patient (Table 3). Variations were found for all dimensions with the five sociodemographic variables mentioned above. The physical mobility section stands out as the section in which most discordances occur proportionately. When moving from cross-tabulations to the calculations of weights and comparing the weights obtained for each SEG in the physical mobility section, the weights obtained for SEG4 are statistically different only from those obtained for SEG2 and SEG3 (Tables 4 and 5). The question of the selection of an appropriate level of significance to elicit acceptable differences, especially in the domain of perceived health should be addressed at this point. Rosser and Kind have argued that “In any analysis which involves repeated testing of new data there must be some degree of caution about the extent to which any significant difference may have occurred by chance” and said that “If we place confidence in all the significant findings at the 5% level, we may underestimate the extent to which there is social consensus’* [14]. Here, significant differences were found for 31 of the 115 pairs at the 5% level of significance. This level reveals more differences than when the 2% level is used (9 discordant pairs) and fewer than when the 8% level is used (42 discordant pairs). This means that, using a 5% level, a lower level of consensus is found than when using a 2% level, and hence the validity of the weights for the general population is less satisfactory. Owing to this particular field of health perception, and more strongly, to the danger of ‘putting on the market’ an instrument with such an attractive feature as a synthetic figure (a unique score by section), we felt the choice of the 5% level of significance was not unfair to the instrument. If one were to adopt a l/1000 level of significance, no difference would be indicated and one could confidently conclude that there are no variations in state of health valuation by Table 5. Differences in weight for the physical mobility section, Spearman’s rank correlation coefficient Comparison of A/B SEG SEG SEC SEG SEC SEG SEG SEG SEG SEG
I/all SEG Z/all SEG 3/ail SEG 4/ail SEG I/SEG 2 I/SEG 3 I/SEG 4 2/SEG 3 Z/SEG 4 3/SEG 4
Correlation coefficient
D2
0.95 0.95 0.95 0.81 0.83 0.93 0.86 0.93 0.69 0.7 I
4 4 4 I6 I4 6 I2 6 26 24
For alpha = 5% and n = 8: R = 0.74.
9.92 10.59 9.92 13.69 II.46
12.05 13.33 13.52 14.09 13.82
9.19 13.10 13.17 9.30 12.02
14.28 12.84 14.96 13.03 13.71
8 29.98 20.38 18.95 17.32 19.28
age, sex, etc. Such a conclusion, when using the instrument in population surveys, would not be neutral and lead to aggregate in a NHP score a socioeconomic component and a purer distress component which is only what the NHP is supposed to pick up. In fact, it is the question of the p risk (lack of power) which should be addressed here rather than the question of the a risk (risk of error). The question is not so much to reject the null hypothesis (null hypothesis = there is no difference), with a risk of a%, when it is true, than to accept it when it is false with a risk of /?“/o. The elucidation of differences in judgement brings into question the use of Thurstone’s method of paired comparisons for weighting the French items of the ISPN. The underlying assumption is that people are able to express a preference for one health state as opposed to another which may not be appropriate in all cultures. Whether judges, in this case French judges, were able to choose the more serious of two subjective expressions of health problems is a central issue. The reactions of the judges were noted by the interviewers. Some judges found the interviews for the pain, physical mobility and emotional reactions sections too long (28, 28 and 36 pairs respectively). Some judgements evidently were difficult to make, notably in the pain, physical mobility, energy and sleep sections. Also, the notion of a ‘general view’ of the health statements was not grasped easily by ail the judges. These difficulties may have lead subjects to decide at random and this could well be a factor contributing to these inter-group variations. Kind [15] has criticized the use of this method of weighting the NHP on the grounds that (i) judges ratings are possibly inconsistent, (ii) there is a lack of psychological continuum in the sleep section and (iii) there are items with similar scale values. Hunt et al., on the other hand, questioning whether perceptions are indeed logical, make a case for retaining the item referring to sleeping tablets as this is perceived as a health problem and also affects the responses to the other items [3, pp. 92-931. They also point out that, in contrast with classical psychological scaling, when scaling in perceived health two statements describing different problems may be judged to be of similar severity by a patient panel. Kind had also noted that an alternative statistical model produced different weights: however, subsequent examination of this situation led Hunt to conclude that the Thurstone method for weighting perceived health statements was preferable [3, p. 951 as a means of obtaining lay judgements of the comparative severity of subjective statements of health problems. Furthermore, the principle of seeking an evaluation of the relative severity of the items is coherent with the philosophy of the instrument.
The French version of the NHP
835
CONCLUSION
The weighting
study has provided a means of validating the translation of the NHP items into French. The comments made during the course of the interviews neither reflected upon the understanding nor on the familiarity of the expressions, confirming the immediate intelligibility of the French version. It cannot be determined whether the few major differences in rank which were found were a result of ‘cross-cultural’ differences in perception and judgement, were indicative of problems of exact equivalence in translation or were simply the outcome of
random variation in response. Although there is a high level of agreement in the weighting of the NHP items, there is nevertheless a non-negligible contribution of sociodemographic characteristics in the generation of items weights. The present authors warn future users of the ISPN to be wary of the use of weights, as they stand, and to complement their results with other expressions of information contained in the instrument which, indeed, is precious (percentage of items responded positively, per section or on the whole, simple addition of positive responses . . . ). Certainly, the generation of specific weights for each of the vast number of sociodemographic sub-groups in the population is not feasible and, even if possible, would exclude comparability [ 161. Overall, the study suggests that, in this translation and adaptation process, the concern about comparability of items weights between sociodemographic groups, SEG in particular, predominates over the concern about cross-lingual comparability. The results have implications for the projects considering adapting the NHP into other European languages. Further studies on the British and Swedish data sets would shed light on this crucial problem in the future of comparative health measurement at the European scale. These results could also prompt the Spanish team to consider a modified sampling frame to conduct to calculation of Spanish weights. Acknorledgemenrs-The project for the adaptation of the Nottingham Profile into French was financed by the Economic and Social Research Council, the Institut National de la Sante et de la Recherche Medicale (INSERM, Grant No. 86.8.014). the Assistance Publique de Paris and the Mission Recherche Experimentation. The authors are grateful to Sonja Hunt, Sarah Curtis and Alain Colvez for their support and advice.
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