ORIGINAL ARTICLE

The psychometric characteristics of an assessment instrument for perceived harmfulness in adolescents with musculoskeletal pain (PHODA-youth) J.A. Verbunt1,2, A. Nijhuis1,2, M. Vikström3, A. Stevens4, N. Haga2,5, J. de Jong1, M. Goossens1,3 1 2 3 4 5

Department of Rehabilitation Medicine, Research School CAPHRI, Maastricht University, The Netherlands Adelante Centre of Expertise in Rehabilitation and Audiology, Hoensbroek, The Netherlands Department of Clinical Psychological Science, Maastricht University, The Netherlands Faculty of Health, Zuyd University of Applied Science, Heerlen, The Netherlands Libra Rehabilitation Medicine and Audiology, Tilburg, The Netherlands

Correspondence Jeanine A. Verbunt E-mail: [email protected] Funding sources This study was funded by Fonds Nuts Ohra. Conflicts of interest None declared. Accepted for publication 27 August 2014 doi:10.1002/ejp.592

© 2014 European Pain Federation - EFICâ

Abstract Background: Cognitive–behavioural models of chronic pain predict that dysfunctional assumptions about harmfulness of activities may maintain pain-related fear and disability. To assess perceived harmfulness in adolescents, the Photograph Series of Daily Activities for youth (PHODA-youth) was developed. Information concerning its methodological quality is currently lacking. Objective: To investigate psychometric characteristics (factor structure, test–retest reliability, construct validity) and feasibility of the PHODA-youth in adolescents with chronic musculoskeletal pain. Study design: Test–retest design. Study population: Adolescents aged 13–21 years with chronic nonspecific musculoskeletal pain. Methods: Participants filled in an electronic version of the PHODA-youth including 89 items twice with a 4-week interval. The instrument’s factor structure was determined by a factor analysis. Construct validity was studied with criterion variables: catastrophizing (Pain Catastrophizing Scale for Children), pain intensity (visual analogue scale), depression (Children’s Depression Inventory) and pain-related disability (Functional Disability Inventory) using regression analysis. Test–retest reliability was evaluated based on the Pearson correlation coefficient. Feasibility was studied with self-constructed questions. Results: Seventy-one adolescents participated. Results show a three-factor structure for the PHODA-youth including 51 items with subscales labelled as: ‘activities of daily life’, ‘intensive physical activities’ and ‘social activities’. Total and subscale scores showed a high internal consistency. Its test–retest reliability was good (r = 0.94) and its construct validity is supported by the finding that both catastrophizing (β = 0.25; p = 0.02) and disability (β = 0.71; p < 0.001) were uniquely related to the PHODA-youth. In addition, feasibility appeared adequate. Conclusion: The findings support the PHODA-youth as a valid and reliable measure of the perceived harmfulness of activities in adolescents with musculoskeletal pain.

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What’s already known about this topic? • Fear of pain is a disabling factor in adults but also in adolescents with chronic pain. What does this study add? • The study reports on the development and psychometric properties of the PHODA-youth, a measure for perceived harmfulness in adolescents with chronic pain.

1. Introduction Pain is common among children: About 25% of children and adolescents report pain in daily life (Perquin et al., 2000; Eccleston et al., 2006a). For about 40% of children with persisting pain for at least 3 months, pain has a considerable disabling impact (Konijnenberg et al., 2005). In adults, the fear-avoidance model has been introduced to explain the disabling role of painrelated fear (Vlaeyen and Linton, 2000) and has been confirmed by numerous studies (Vlaeyen and Linton, 2000, 2012; Verbunt et al., 2003; Leeuw et al., 2007a). It states that highly fearful persons who tend to think in catastrophes will avoid activities they perceive as harmful or pain provoking. In the long term, this avoidance behaviour can result in disability and depression, further fuelling the vicious circle of disabling musculoskeletal pain. This disabling effect of pain-related fear on the ability to perform physical activities/movements has recently also been confirmed in adolescents with pain (Eccleston et al., 2008; Simons and Kaczynski, 2012). In a study of Cohen et al. (2010), it appeared that, in adolescents with chronic pain, anxiety acted as a moderator in the association between pain and both physical and social functioning. In highly anxious adolescents, anxiety instead of pain appeared to be associated with restrictions in social and physical functioning (Cohen et al., 2010). Restrictions in physical abilities can have direct negative effects on opportunities for social exposure and developmental experience (Yoder, 2000; Eccleston et al., 2008). In this phase of life, being fearful and in pain can thus restrict not only current functioning but also future functioning. To study various aspects of fear in adolescent pain, adequate assessment is essential. Recently, two new assessment instruments to measure the construct ‘pain-related fear’ in adolescents came available: the fear of pain questionnaire (Simons et al., 2011) and the paediatric pain fear scale (Huguet et al., 2011). Both instruments facilitate the study of pain-related 696 Eur J Pain 19 (2015) 695--705

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fear in adolescent pain. However, these instruments do not specify/select those activities/situations perceived as harmful in an individual adolescent. This specific information is important in an intervention aimed at reducing pain-related fear, such as in graded exposure. For adults, for this purpose, the Photograph Series of Daily Activities (PHODA) has been developed, including a set of pictures of various movements/daily activities (Leeuw et al., 2007b). The PHODA is used as an assessment instrument to measure perceived harmfulness, or the indication of the patient to what extent he/she perceives the activity to be harmful for the painful body part. In adults, the PHODA has good psychometric properties (Leeuw et al., 2007b). Recently, we developed an adolescent PHODA version (PHODA-youth) incorporating age-specific activities and social situations. The aim of the current study is to investigate the psychometric characteristics of the PHODA-youth. We hypothesize that the PHODA-youth instrument will be a valid (based on adequate construct validity) and reliable (based on adequate factor structure, internal consistency, test–retest reliability) instrument to measure perceived harmfulness of activities in adolescents with chronic musculoskeletal pain.

2. Methods and materials 2.1 Design The study has a test–retest design, with a 4-week interval in between. Its factor structure was defined and the following psychometric characteristics were tested: reliability (internal consistency and test–retest reliability) and validity (construct validity). In addition, the feasibility of the instrument was tested.

2.2 Participants A total of 71 adolescents and young adults were included in this study during the inclusion period from April 2010 to October 2011. Inclusion criteria were: (1) belonging to the age 12–21 years; (2) suffering from a chronic pain syndrome (musculoskeletal pain syndrome, generalized pain syndrome, fibromyalgia, complex regional pain syndrome) with duration over 3 months; and (3) not diagnosed with a specific somatic (rheumatoid, neurological and orthopaedic) disorder that could explain the current pain problem. Patients who were not able to understand the Dutch language were excluded from participation in the study. In addition, patients receiving a behavioural intervention (as a single psychological treatment or a rehabilitation programme) during the 4-week interval between the two assessment moments could partici© 2014 European Pain Federation - EFICâ

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pate in the first assessment but were excluded for follow-up assessment in order to ensure stability of the variable under measurement during the study period. The spectrum of 12–21 years of age was used according to Kaplan, who defines a start of early adolescence at 12 years and a completion of this life stage with the ending of late adolescence at the age of 21 years (Kaplan, 2004).

38 patients participated in both assessment moments. An overview of the inclusion of all persons is presented in Fig. 1. The Medical Ethical Committee of the Maastricht University Medical Centre approved the study protocol (NL311292.068.10).

2.4 Measures 2.3 Procedure Adolescents and youngsters were found for participation in the study in three different ways. First, adolescents were informed by a consultant in rehabilitation medicine in one of the participating rehabilitation centres when they attended the consultation hour. All potential participants (and their parents in case the patient was below 18 years of age) received an information letter from their consultant in rehabilitation medicine, who checked the inclusion criteria in advance. Forty-three participants were included based on this first inclusion route. Of these, 28 persons started a behavioural rehabilitation programme within 4 weeks and participated therefore only during the first assessment, which was a pretreatment assessment. Second, adolescents and youngsters who participated in an earlier study (Stommen et al., 2012) and who indicated that they were willing to participate in future research activities were sent an information letter about the current study after the inclusion criteria were checked by the consultant in rehabilitation medicine. Sixteen of the 36 persons who were sent an invitation letter based on inclusion route 2 agreed to participate. Third, adolescents and youngsters who were members of a Dutch patient organization for patients with fibromyalgia were sent an information letter. Only patients who confirmed that fibromyalgia was diagnosed by a physician were included. Twelve of the 62 persons who received an information letter based on inclusion route 3 eventually decided to participate. The combination of inclusion routes resulted in the participation of adolescents with pain with a variety of disability levels (both patients without current care and patients who consulted specialized care due to perceived problems were included). After these adolescents showed an interest in the study, they were contacted by telephone. The parents of those adolescents aged below 18 years had to confirm that they agreed with participation and had to sign the agreement form together with the adolescent. If adolescents and young adults were indeed willing to participate, a participation information form was sent to the child and the parents; this form contained a login code that enabled the participant to enter the web-based PHODA-youth programme for the current study. After inclusion, the adolescents were invited to fill in a web-based questionnaire containing the first assessment procedure of the current study. After 4 weeks, all participants received an e-mail with an invitation to complete the second questionnaire. In summary, a total number of 71 persons participated in the study. Five persons stopped before total completion of the first assessment. In addition, © 2014 European Pain Federation - EFICâ

During the first assessment, participants were asked to fill in: (1) the new instrument – PHODA-youth; (2) a set of questionnaires representing the criterion variables in order to study the instrument’s construct validity; and (3) a set of questions assessing the feasibility of the PHODA-youth programme. The second assessment, which was performed 4 weeks after the first assessment and was aimed at studying the instrument’s test–retest reliability, included the PHODAyouth only. Both assessments were web based, which enabled the participant to complete the questionnaires at home. The procedures of the first and second assessments were completely identical, with the only exception that the first assessment included more questions. The first and the second assessments were independent from each other: During the second assessment, patients were not able to check the scoring of their first assessment. In both digital questionnaires, participants had to fill in all items to be able to continue to the next part of the questionnaire. Of patients who stopped before completion, all available items were used in the analysis. Participants were able to e-mail a research assistant in case they needed technical help with entering the digital system.

2.4.1 Sociodemographic and medical variables In order to describe the population under study, the following variables were recorded: age, gender, duration of pain, education and absence from school.

Inclusion route 1: 77 persons

43*

Inclusion route 2: 36 persons

16

Inclusion route 3: 62 persons

12

Assessment 1: 71 participants

Assessment 2: 38 participants Figure 1 Inclusion of patients in the study. *In inclusion route 1, 28 persons participated in the first assessment only, due to a start of a rehabilitation programme.

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Figure 2 A representation of the digital version of the PHODA-youth.

2.4.2 PHODA-youth 2.4.2.1 Summary of the development of the PHODA-youth to be tested The point of departure in the development of the PHODAyouth consisted of a list of 171 activities, relevant for adolescents and young adults aged 12–21 years and which was derived from a literature review. Out of this list, a representative group of healthy adolescents selected a total of 142 activities and social situations as relevant for this stage of life (Janssen et al., 2009). Furthermore, focus-group interviews with 12 adolescents with chronic musculoskeletal pain identified an additional 15 activities and social situations, which resulted in a total list of 157 items for the PHODA-youth. This 157-item list was consecutively presented to a Delphi panel of 35 Dutch experts in adolescence chronic pain rehabilitation (consultants in rehabilitation medicine, physiotherapists, occupational therapists and researchers on the domain of children and pain). The Delphi-panel participants scored for all items: (1) whether the activity/situation would be disabling for adolescents with chronic musculoskeletal pain; and (2) whether the activity/situation would be fear provoking for this population. Items with a positive answer for both questions as scored for at least 70% of the participants were selected for further evaluation. Two Delphi rounds were needed. Based on the input of the Delphi panel, a total number of 89 activities and social situations were then identified and were included in the concept version of the PHODA-youth. A professional photographer made pictures of all 89 activities and situations. 698 Eur J Pain 19 (2015) 695--705

2.4.2.2 The concept version of the PHODA youth (PHODA-youth-C) The concept instrument included 89 pictures representing activities and situations with the potential to be perceived as harmful by adolescents with chronic pain. The project group categorized these items in the following seven categories of the PHODA-youth-C: (1) self-care activities of daily living (ADL)/eating and drinking; (2) self-care – household activities; (3) transport and other activities; (4) school/study/ work; (5) sport activities; (6) specific movements in sports; and (7) social and leisure time activities. All selected activities and situations were presented on a picture and were included in the PHODA-youth-C. An example is given in Fig. 2.

2.4.2.3 Assessment procedure of the PHODA-youth The participant, sitting in front of a computer monitor was exposed to all PHODA pictures on the computer screen in a fixed order. The following instructions were given before the first picture appeared: ‘Please observe each picture carefully, and try to imagine yourself performing this activity/ movement. How harmful do you think that this movement/ situation will be because of your pain?’ Consecutively, the participant was requested to drag each picture (representing one of the activities/situations) along a ‘harmfulness scale’ ranging from 0 (‘not harmful at all’) to 10 (‘extremely harmful’), with 100 scoring possibilities in between. The pictures could be positioned on the scale based on an interactive programme. Each picture was automatically scored according to its position on the scale. Due to the electronic © 2014 European Pain Federation - EFICâ

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administration, the processing of the assessment procedure is standardized and the data are automatically stored into an electronic database. The basic properties of the original PHODA for adults (such as the instruction, the possibility for the patient to move the pictures along the harmfulness scale at any time and the fact that all pictures remain visible along the scale) (Leeuw et al., 2007b) were maintained in the procedure of the PHODA-youth. To obtain subscale scores, scores on all items in the subscale were summed. For the total score, all items were summed.

2.4.3 Pain catastrophizing scale Catastrophic thinking about pain was assessed with the Dutch version of the Pain Catastrophizing Scale for Children (PCS-C; Crombez et al., 2003). This instrument consists of 13 items describing different thoughts and feelings that children may experience when they are in pain. Children rate how frequently they experience each of the thoughts and feelings when they are in pain using a 5-point scale (0–4). Total scores are obtained by summing the ratings for each item. The PCS-C has shown to be a reliable and valid instrument for children (Crombez et al., 2003).

ment consists of 15 items concerning perceptions of activity limitations during the past 2 weeks. The items are rated on a 5-point scale (0–4). Total scores are obtained by summing the ratings for each item. Higher total scores indicate greater disability. The reliability and validity have been demonstrated in research in adolescents (Walker and Greene, 1991; Claar and Walker, 2006; Eccleston et al., 2006b; Kashikar-Zuck et al., 2011).

2.5 Feasibility After completion of the PHODA-youth during the first assessment, the following three self-constructed questions including answer categories were presented to the participants: (1) ‘Was the instruction clear for you?’ (yes/no). (2) ‘How would you rate the size of the pictures?’ (‘much too small’, ‘too small’, ‘adequate’, ‘too large’, ‘much too large’). (3) ‘Did the PHODA contain difficult words that you didn’t understand?’ with answer categories: (yes/no). In addition, participants had the possibility to provide additional information concerning their opinion on the PHODA-youth on a blank space.

2.4.4 Pain intensity (VAS) The intensity of current pain was assessed with a 10-cm visual analogue scale (VAS) with the endpoints ‘no pain’ and ‘worst pain I can imagine’. The pain-severity VAS has a good reliability and validity in children (McGrath, 1987).

2.4.5 Children’s depression inventory Depressive symptoms were measured by the Dutch version of the Children’s Depression Inventory (CDI; Kovacs, 1981). The CDI is a self-report inventory that assesses symptoms of depression in children and adolescents. It contains 27 selfreport items on five subscales (negative mood, interpersonal problems, ineffectiveness, anhedonia, negative self-esteem), representing depressive symptoms. Each item is rated on a three-point scale and summed to obtain a total score. Higher scores indicate higher levels of depressive symptoms. The CDI has been found to have acceptable reliability and good validity in children and adolescents (Smucker et al., 1986; Claar and Walker, 2006; McCracken et al., 2006; Roelofs et al., 2010).

2.4.6 Functional disability inventory Pain-related disability was assessed with the Dutch version of the Functional Disability Inventory (FDI; Walker and Greene, 1991). The FDI is a self-report inventory for children measuring perceived difficulty in performing a number of activities in the domains of school, home, recreation and social interactions. It is designed to be applicable to a broad range of illnesses and varying levels of severity. The instru© 2014 European Pain Federation - EFICâ

2.6 Statistical analysis The following psychometric characteristics of the PHODA youth instrument were investigated: Factor structure and internal consistency: All 89 items were included in the analysis. First, the most clinically relevant item of those two items that correlated >0.85 was selected for further analysis (Field, 2009). Second, three different methods were used to determine the number of factors: (1) ‘Kaiser’s eigenvalue-greater-than-one rule’ (Kaiser, 1960); (2) inspection of the screen plot; and (3) inspection whether the factors were meaningful. Third, a principal component analysis was performed to determine the eventual number of items within each factor. Items that loaded 0.4 or higher were included in the final factor (Field, 2009). The Kaiser– Meyer–Olkin measure, representing the ratio of the squared correlation between variables to the squared partial correlation between variables, is used to indicate sampling adequacy. For each factor found, a scale was created and consecutively a Cronbach alpha for that scale was calculated to assess its internal consistency. In addition, the Cronbach alpha for the total scale was calculated. Test–retest reliability: The Pearson correlation coefficient was calculated. In addition, the stability of the PHODAyouth was studied by testing the equality of the mean scores of both measurements by the paired t test, and by checking the equality of the variances at both time points. Construct validity: The construct validity of the PHODAyouth was investigated based on its hypothesized positive association with the criterion variables [pain catastrophizing (PCS-C), functional disability (FDI), depression (CDI) and Eur J Pain 19 (2015) 695--705

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current pain intensity (VAS)]. Associations were tested based on Pearson correlation coefficients. A Bonferroni correction was applied for multiple testing. Furthermore, to adjust for common variance between constructs, a multiple linear regression analysis was performed with the PHODA-youth as the dependent variable and the PCS-C, VAS pain intensity, CDI and FDI as independent variables. Collinearity control included checking variable inflation factors (VIFs), which had to be below 10. All analyses were performed using SPSS software version 17 (IBM, Chicago, IL, USA).

3. Results 3.1 Sociodemographic and pain-related variables Demographic and pain-related variables characteristics of all participants are presented in Table 1. Participants had a mean score of 49.3 (SD = 26.2) for pain Table 1 Demographic and pain-related characteristics (N = 71). Gender (N, % female) Age (years) Current educational level (N, %) Elementary school High school ( lower level) High school (intermediate level) High school (high level) University Missing Current school/work participation: In school (N, %) Absence from school during the last year (N, %) 0–14 days 15–30 days 1–3 months >3 months Unknown Paid job (N, %) Absence from work due to sick leave (N, %) Without a paid joba Disability pension Unknown Pain related variables Duration pain complaints (years) Type of pain problem (N, %) Generalized pain syndrome/fibromyalgia/ hypermobility syndrome Chronic pain syndrome lower extremity Chronic pain syndrome upper extremity Back pain syndrome/whiplash Complex regional pain syndrome Unknown Other family member with chronic pain (N, %) a

65 (91%) 17.0 ± 3.0 11 (15.4) 18 (25.4) 25 (35.2) 5 (7.0) 11 (15.5) 1 (1.4) 54 (76) 25 (46) 12 (22) 9 (17) 7 (13) 1 (2) 8 (11) 2 (25) 5 (7) 2 (3) 2 (3) 4.3 ± 3.9 36 (51) 11 (15) 4 (6) 15 (21) 3 (4) 2 (3) 37 (52)

Two persons without a job scored their school absence (before quitting school) over the last year.

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intensity, 21.0 (SD = 12.3) for catastrophizing, 11.1 (SD = 6.8) for depression and 22.3 (SD = 10.7) for pain-related disability.

3.2 Psychometric properties of the PHODA-youth 3.2.1 Factor structure and internal consistency The factor analysis revealed three factors with a factor loading of the individual items as presented in Table 2. The Kaiser–Meyer–Olkin measurement was 0.73 and Bartlett’s test of sphericity was significant (p < 0.001). Based on this factor analysis, 51 items remained in the PHODA-youth. Three PHODA-youth factors could be identified: (1) activities of daily life (13 items); (2) intensive physical activities (27 items); and (3) social activities (11 items). The explained variance of the total PHODA-youth was 62.05%, and it was 10.72%, 44.49% and 6.84% for the three factors, respectively. The internal consistency of the total score on the PHODA-youth was 0.98. The internal consistency of the three PHODA-youth subscales was 0.94 for subscale 1 ‘activities of daily life’, 0.97 for subscale 2 ‘intensive physical activities’ and 0.90 for subscale 3 ‘social activities’. Mean PHODA-youth scores are: 228.6 (SD 113.4) for the total score; 47.4 (SD 33.7) for the activities of daily life subscale; 149.8 (SD 70.9) for the intensive physical activities subscale; and 30.7 (SD 23.3) for the social activities subscale. No age-related differences for adolescents below 19 years of age and those of 18 years and above appeared to be present (activities of daily life subscale p = 0.09, intensive physical activities subscale p = 0.98 and social activities subscale p = 0.36; PHODA-youth total score p = 0.46). 3.2.2 Test–retest reliability The Pearson correlation between both PHODA-youth measurements was 0.94 (p < 0.001). Both scores did not significantly differ from each other (t = 0.26, p = 0.79). In addition, first and second assessments on all three subscales did not differ significantly, with: t = −0.15, p = 0.88 for scale 1; t = 0.65, p = 0.52 for scale 2; and t = −0.3, p = 0.77 for scale 3. 3.2.3 Construct validity Associations between the PHODA-youth including its subscales and the construct variables are presented in Table 3. Since 28 associations have been tested, a Bonferroni correction resulted in a level of significance of © 2014 European Pain Federation - EFICâ

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Table 2 The PHODA items and three-factor structure. Factor loadinga PHODA item To cut meat/bread To open/close a jar/cap of a bottle Doing the dishes Hair care (blow dry, style, putting in gel) Putting on/off shoes with shoelaces Putting pants on Stepping in/out the bathtub To unload to fill/empty the dishwasher To make the bed To go grocery/shopping Playing an instrument Cleaning own room Vacuuming Running Team ball sports Tennis and other racket sports To break your fall Dancing/sports Participating in PE/gym Pushing against an object/opponent To push up Jumping over something Biking Dancing Kicking a ball Cycling with a back pack Strengthening/physical fitness Part-time job Making a trip e.g. going to an amusement park To lift (lifting) heavy things with two hands Walking upstairs/downstairs Throwing a ball or other objects Walking in school/moving around in and around school (stairs/busy corridor) Cycling to school/work with friends To be in school for the whole day Swimming Carrying a heavy backpack Standing Walking Balancing on one leg Being out with friends Going to the movies Visiting friends and family Being outside with friends To plan activities with friends/(making plans) Travelling/going on vacation Writing or sitting at a desk Travelling by car Doing your home work Travelling by public transport Shopping/going to the mall a

1 2 3 4 5 6 7 8 9 10 11 12 13 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 1 2 3 4 5 6 7 8 9 10 11

Mean (SD)

Daily life

1.92 (2.87) 3.29 (3.58) 3.32 (3.29) 2.66 (2.93) 2.82 (2.87) 2.54 (3.00) 2.42 (2.97) 2.84 (3.09) 4.23 (3.56) 3.74 (3.16) 3.18 (3.30) 4.16 (3.10) 4.90 (3.20) 6.22 (3.56) 6.89 (3.24) 6.95 (3.27) 6.97 (3.33) 6.00 (3.26) 7.11 (3.24) 6.24 (3.60) 6.72 (3.50) 5.66 (3.36) 5.76 (3.42) 5.73 (3.41) 5.35 (3.45) 5.37 (3.55) 6.08 (3.38) 5.18 (3.60) 5.19 (3.15) 5.93 (3.25) 4.67 (3.25) 5.56 (3.55) 4.66 (3.51) 4.64 (3.62) 5.37 (3.50) 4.10 (3.43) 5.48 (3.58) 4.05 (3.29) 4.23 (3.21) 3.83 (3.27) 1.69 (2.64) 2.29 (2.70) 2.16 (2.75) 2.23 (2.86) 2.57 (2.86) 3.60 (2.97) 2.75 (2.88) 2.74 (2.88) 3.09 (3.21) 3.40 (3.10) 4.30 (2.91)

0.92 0.88 0.76 0.75 0.75 0.65 0.59 0.59 0.58 0.53 0.50 0.46 0.43

Physical

Social

0.96 0.96 0.90 0.86 0.86 0.85 0.80 0.75 0.82 0.78 0.77 0.75 0.73 0.69 0.68 0.68 0.65 0.62 0.61 0.58 0.56 0.55 0.54 0.54 0.54 0.49 0.49 0.90 0.82 0.79 0.75 0.62 0.56 0.55 0.55 0.53 0.51 0.44

A factor loading of 0.4 or more is considered as a satisfactory factor loading (Field, 2009).

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Table 3 Association between PHODA-youth and construct variables. 1 1. PHODA-youth Total score 2. PHODA-youth Factor ADL 3. PHODA-youth Factor intensive physical activities 4. PHODA-youth Factor social activities 5. Pain intensity (VAS) 6. Disability (FDI) 7. Catastrophizing (PCS) 8. Depression (CDI)

2

3

4

5

6

7

8

– 0.455*** 0.407*** 0.337**

– 0.515*** 0.578***

– 0.597***



– 0.812***



0.947***

0.620***



0.794***

0.629***

0.638***



0.437*** 0.771*** 0.530*** 0.415**

0.361** 0.542*** 0.465*** 0.341**

0.451*** 0.746*** 0.444*** 0.359**

0.284* 0.671*** 0.555** 0.429***

Bonferroni level of significance: 0.0018. The bold names are the variables that belong to the new developed instrument. *p = < 0.05. **p = < 0.01. ***p = < 0.001.

0.05/28 = 0.0018. As presented in Table 3, even after correction, most associations reached the level of significance. The results of the multiple regression analysis indicated that the explained variance of the model was R2 = 0.65. Perceived harmfulness as measured with the PHODA-youth was significantly associated with the level of disability (β = 0.71; p < 0.001) as well as the level of pain catastrophizing (β = 0.25; p = 0.02) but not with pain intensity (β = 0.04; p = 0.66) and depression (β = −0.12; p = 0.25). All VIFs remained below 10.

3.3 Process evaluation All except one (98%) adolescent indicated the instruction as clear. Sixty (91%) perceived the extent of the pictures as adequate, one (1%) as much too small and five (8%) as much too large. All except one (98%) indicated that the PHODA-youth contained no difficult words. The following quotes were presented on the blank space. Seven persons (11%) indicated that an activity presented on a picture that they did not do themselves was confusing. A specific example mentioned was ‘driving a scooter’. One person (1%) reported avoiding activities due to another medical complaint instead of pain. One person (1%) reported that dragging the pictures was irritating for his/her hands. Four persons (6%) indicated that they needed assistance due to technical problems before they were able to complete the assessment.

4. Discussion The aim of this study was to investigate the psychometric characteristics of the PHODA-youth as a 702 Eur J Pain 19 (2015) 695--705

measure of perceived harmfulness of daily activities in adolescents with musculoskeletal pain. The results of this study revealed that the PHODA-youth measures three factors to assess perceived harmfulness of activities: (1) ADL and household; (2) intensive physical activities; and (3) social activities. It consists of a total of 51 items. The test–retest reliability over a 4-week time interval is excellent, and its construct validity is supported by significant relationships with catastrophizing and disability. Our study population relates to other populations of adolescents with chronic pain. The mean disability level (FDI = 22.3) seems comparable to samples from a hospital/pain clinic (Simons et al., 2011 [FDI = 23.6; SD = 11.8]; Stommen et al., 2012 [FDI = 20.4; SD = 11.7]; but is lower as compared to children attending intensive rehabilitation [FDI = 32; SD = 10.3] Simons et al., 2012). In addition, the mean level of catastrophizing (PCS-C = 21.0; SD = 12.3) is the same as in other pain populations (Stommen et al., 2012; PCS-C = 20.4; SD = 11.7) but higher as compared to the general adolescent population (PCSC = 16.8; SD = 8.8; Crombez et al., 2003). Three PHODA-youth factors were identified that best represented the themes activities of daily life, intensive physical activities and social activities. The fact that the intensive physical activities subscale contributed highly to the total variance score seems to indicate that activities especially in this subscale are prone to fear. This could also indicate that adolescents can probably rely longer on alternative movement strategies during performance of activities of daily life and social activities, whereas intensive physical activities need a direct confrontation with fear. Due to fear, performance can be suboptimal or even complete © 2014 European Pain Federation - EFICâ

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avoidance of these activities can occur. As a result, adolescents will especially feel disabled on this domain of functioning. The total score and the three subscales had an excellent value for internal consistency, confirming the alignment of the items within subscales. The broad range of mean scores between items from 1.69 to 7.11 indicates that different activities/ situations were included with various levels of perceived harmfulness, supporting the scoring variation of items within an individual assessment. The finding that, in adolescents, a unique factor, ‘social activities’, could be identified confirmed our hypothesis that, in this life stage, participation in social activities can be prone to pain-related fear. Eventually, 51 of the 89 items are included in the final PHODA-youth version. Analysis revealed that activities/situations that were identified as less applicable by some of the individual adolescents (e.g., driving a scooter) were, as a result of the factor analysis, all excluded from the final PHODA-youth. This seems to support the applicability of the final PHODA-youth set in various pain problems in adolescence. The construct validity of the PHODA-youth is supported by significant correlations with all construct variables. Regression analyses, in which intercorrelations between the construct variables themselves were compensated, revealed that perceived harmfulness was positively associated with catastrophizing and disability. This may indicate that adolescents with high levels of perceived harmfulness in activities tend to catastrophize more. This anxious perception of activities may be associated with a lower level of activities and a higher level of disability. In this, it is however important to consider that we did have activityspecific information on the level of perceived harmfulness in the current study, but scores for disability and catastrophizing were not activity specific. Activity-specific information for the construct variables disability and catastrophizing could have resulted in even higher associations. However, for this validation study, we chose to use questionnaires for our construct variables with confirmed psychometric properties. Since activity-specific questions for disability and catastrophizing are not available/validated, these would have to be self-constructed, which is not an option for a construct variable. Another explanation for the high association between the PHODAyouth score and functional disability could be that the adolescents, despite the careful instruction of the PHODA-youth procedure, misinterpreted the concept of perceived harmfulness and placed the pictures along the thermometer according to the level of disability they perceive. Since the adolescents filled in the © 2014 European Pain Federation - EFICâ

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PHODA-youth online, a final check of their understanding of the concept of harmfulness was difficult to perform. However, the finding that all except one adolescent indicated that the instruction was clear seems to contradict this supposition. In addition, three individual adolescents even discussed the difference between disability and perceived harmfulness spontaneously in the evaluation section, which seems to support their understanding of the concept. In order to represent adolescence, we decided to include persons up to the age of 21 instead of 18 for two reasons. First, in interpreting cognitive and behavioural processes in the ages of 18–21, it is important to realize that in this stage of life, the human brain is still developing (Giedd et al., 1999). Interpretations such as perception on harmfulness can thus still be sensitive to change and can differ from adult evaluations. Second, in the context of the activities/ situations that have to be evaluated for perceived harmfulness, it is important to realize that almost 80% of those in the ages of 15–20 are still mainly focussed on educational activities. In the Netherlands, only 20% of the 15- to 20-year-olds are part of the working population (Statistiek CBS, 2013). Out of this perspective, daily activities will be more in line with activities of younger adolescents instead of those of adults. For this reason, we decided to develop this measure for persons up to 21 years. There are some limitations to be considered. First, although 175 adolescents were invited to participate, only 71 decided to participate. The main reasons for this restricted number of inclusions could be the complex inclusion procedure, the need to meet ethical requirements and little interest in research participation in the phase of adolescence or the online administration of the questionnaire. A restricted number of participants may influence negatively the outcome of the factor analysis. However, the adequate Kaiser– Meyer–Olkin score found supports the factor structure identified within the current research population. Sample size, the level of communalities and the number of factors are all important related to the fit of the factor model in the population (Preacher and MacCallum, 2002). To confirm the three-factor structure of the PHODA-youth, cross-validation among other samples of adolescents with musculoskeletal pain is however recommended. A second limitation could be that the set of construct variables did not include a measure representing the concept of fear of pain. Unfortunately, at the start of this study, no measure for this in adolescents was available. Meanwhile, two instruments, the fear of pain questionnaire (Simons et al., 2011) and the paediatric pain fear scale Eur J Pain 19 (2015) 695--705

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(Huguet et al., 2011) have been published. To further strengthen the validity of the PHODA-youth, it would be worthwhile to study its association with both questionnaires and test its relation with the outcome of behavioural task performance. In addition, its validity would be further supported by a confirmation of its responsiveness related to an intervention with the aim to change perceived harmfulness, such as graded exposure. A third limitation of this study is the underrepresentation of boys in this study. However, this male:female ratio reflects well the gender ratio of the adolescent pain population, since it is in line with other paediatric pain populations (Simons and Kaczynski, 2012; Stommen et al., 2012). As a result, however, generalization of these findings to males has to be performed with caution and needs further study.

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activities/situations in adolescence with chronic musculoskeletal pain syndromes. The reliability and validity of the instrument are adequate, but its responsiveness still needs further study.

Author contributions J.A.V and M.G take responsibility for the integrity of the work as a whole, from inception to published article. M.V., A.S., N.H. and J.d.J. were involved in the development of the study design and the writing process. A.N. was involved in data acquisition and the writing process. All authors approved the final version of the article. The PHODA-youth Dutch version, studied in this project, is available upon request.

Acknowledgements

4.1 Clinical implications The PHODA-youth has the unique ability to identify those individual activities and situations perceived as harmful for the adolescent. The opportunity to create an individual list of activities/situations with a high treat value for the individual adolescent is the optimal input to start a treatment such as graded exposure. Exposure-based treatment seems promising to reduce pain-related fear and disability in adolescents (Wicksell et al., 2007). Assessment of the PHODAyouth can be integrated in the assessment phase of graded exposure treatment in adolescents with pain. In this study, the PHODA-youth was administered as a computerized assessment tool; however, to identify activities/situations perceived as threatening, the instrument can also be used during a clinical interview enabling interaction between the therapist/clinician and patient. In case the original PHODA-youth instruction will be maintained, there is no obvious reason to expect different results in its application as a clinical diagnostic instrument. For research purposes, however, it is advised to use the tool as developed and tested. Future study of an adapted parent version of the PHODA-youth will also give the opportunity to study parental perceived harmfulness. It would be, e.g., of additional value to relate this to the motivation of the parents to stimulate or restrict their children from performing these specific activities. In addition, studying differences in perceived harmfulness of activities between the child and its parents is of interest for research but can also help to discuss perceptions within one family. In conclusion, the PHODA-youth can be used as an assessment instrument for perceived harmfulness of 704 Eur J Pain 19 (2015) 695--705

We would like to thank all participants and consultants in rehabilitation medicine involved in referring patients to this study. In addition, we would like to thank M. Vestjens for programming the concept computer version of the PHODAyouth. We further appreciated valuable comments of Prof. Dr. Madelon Peters, Dr. L. Simons and Dr. G. van Breukelen who helped us to further improve the study. The authors have no conflicts of interest.

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The psychometric characteristics of an assessment instrument for perceived harmfulness in adolescents with musculoskeletal pain (PHODA-youth).

Cognitive-behavioural models of chronic pain predict that dysfunctional assumptions about harmfulness of activities may maintain pain-related fear and...
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