679
development into IQ type differences, even in infancy and early childhood.s Lately, a study of separated identical twins has fully substantiated traditional claims that IQ differences are of mainly genetic origin,6 the genetic influences presumably being mediated by lasting differences in nervous system functioning. Biological and environmental differences probably set up mental speed differences that lead to variations in general ability, tested IQ, and life chances. Even tested IQ differences, which develop towards the end of a complex causal chain, are demonstrably reliable, heritable, and predictive. How, then, can intelligence be so easily considered an illusion? C. R. BRAND P. G. CARYL I. J. DEARY V. EGAN H. C. PAGLIARI
Department of Psychology,
University of Edinburgh, Square, Edinburgh EH8 9JZ, UK
7 George
1. Schwartzman
AE, Gold D, Andres D, Arbuckle TY, Chaikelson J. Stability of intelligence: a 40-year follow-up. Can J Psychol 1987; 41: 244-56. 2. Hunter JE, Hunter RF. Validity and utility of alternative predictors of job performance. Psychol Bull 1984; 96: 72-98. 3. Blaha J, Wallbrown FH. Hierarchical factor structure of the WAIS-Revised. J Consul Clin Psychol 1982; 50: 652-60. 4. Kranzler JH, Jensen AR. Inspection time and intelligence: a meta-analysis. Intelligence 1989; 13: 329-47. 5. Bornstein MH, Sigman MD. Continuity in mental development from infancy. Child Dev 1986; 57: 251-74. 6. Bouchard TJ Jr, Lykken DT, McGue M, Segal NL, Tellegen A. Sources of human psychological differences: the Minnesota Study of twins reared apart. Science 1990; 250: 223-28.
So
long
SIR,-In your editorial of Feb 23 (p 460), you comment that "nobody dies of old age-that is to say, simply through the passage of time". Is this so? Many doctors will have had experience of elderly patients-frail, no doubt, but basically healthy and alert and quite active-who simply "died in their sleep". I have known three such patients, all women, two in their mid-80s and one in her early 90s. To me, people like that, rather than dying, simply stop living. So, the cause of death? To invoke a symptomless myocardial infarction in the absence of any evidence for it is clearly wrong. Admittedly, serial 5 fim sections of the whole of the brain and heart might reveal a cluster of cells that had undergone dissolution from the collapse, for some reason at some time, of some organelle. Then, after international agreement on the nature of the syndrome, the individual could be said to have died from this novel "disintegration xyz" rather than "old age". A search on this scale is impracticable so, in these circumstances, what explanation remains but old age? Your editorial refers later to a "fundamental interference with the
species ’clock’, which determines potential lifespan". I submit that it is precisely this fundamental interference, nature as yet unknown, that allows some fortunate people to die just of old age-and what a dignified entry that makes on a death certificate. Gowranes, Kinnaitd PH14 9QY, UK
WALLACE PARK
What do doctors know of statistics? SIR,-Dr Dodwell (Feb 16, p 432) raises an issue of concern when he asserts that "it is easier for a doctor to build up his personal statistical toolkit than for a statistician to attain sufficiently illuminating medical knowledge". Statisticians and doctors alike will recognise his satirical caricature of a consultation beween them. The question, however, is whether psychiatrists have devised more illuminating answers than those of the apocryphal statistician: if they have, they ought to let someone know, for statisticians have long sought the elixir that apparently resides in Dodwell’s toolkit. The ideal he recommends, exemplified by junior pyschiatric doctors receiving an education in research methodology, is worrying in the light of the research of Wulff et al.1 Medical participants in a course on postgraduate research methods scored a median of 4-0 correct answers out of 9 multiple choice questions relating to the understanding of elementary statistical expression (SD, SE, p < 0-05, p > 0 05, and r). These doctors would have found
less comfort from a senior colleague than from a hospital statistician for statistical advice-the median score dropped to 2-4 in a random sample of doctors, and the median was 2-1 among those who had qualified more than 15 years ago. The conclusion was that "the statistical knowledge of most doctors is so limited that they cannot be expected to draw the right conclusions from those statistical analyses which are found in papers in medical journals". Collaboration between doctors and statisticians has provided the scientific basis of contemporary medicine, and an increased knowledge of statistics among doctors can only improve the chances of fruitful communication. Before Dodwell advocates the scornful dismissal of expert advice in favour of the sparse contents of a personal toolkit he should consider something that Oscar Wilde actually did say: "The truth is seldom pure and never simple". Social Paediatric and Obstetric Research Unit, University of Glasgow, Glasgow G12 8RZ, UK
A. H. LEYLAND
C. W. PRITCHARD
1. Wulff HR, Anderson B, Brandenhoff P, Guttler F. What do doctors know about statistics? Stat Med 1987; 6: 3-10.
Assessment of risks and control in
occupational infection SIR,-Professor Scully and Dr Porter (Jan 19, p 178) refer to my general practice decontamination study’ as showing "poor" infection control in general practice. Rather, we reported a surprisingly large increase in autoclave ownership by UK general practitioners (49% of practices), compared with 8%2 and 25%3 of practices reported a year earlier. Many of our respondents indicated that they were planning to purchase an autoclave, and if our findings reflected a true increase in ownership over time then it is likely that more than three-quarters of general practices are now equipped with effective steriliser systems, as recommended by the British Medical Association (BA4A).’A follow-up study will be undertaken to reassess autoclave ownership and compliance with other infection control measures, such as glove use. Scully and Porter also raise the very important issue of hepatitis B vaccination for medical students. They report that as a matter of course dental students are vaccinated before qualification. There are about 8000 clinical medical students in the UK for whom vaccination should also be standard policy, as recommended by the BMA. S,6However, not all medical schools and hospital authorities accept this recommendation and educational programmes continue to be needed to raise awareness among clinical students, doctors, nurses, and other health care professionals. Risk assessment in clinical practice is an underestimated and vitally important matter. The risk of infection after needlestick injury with a sharp item contaminated with HIV-positive blood is substantial (1 in 200) and may relate to the amount of blood (and infectious virions) transferred during injury.’ Hepatitis B infection, however, is a far more likely risk (6-20%) after needlestick exposure, and hepatitis C risk has yet to be estimated but might be similar. I have piloted a simple interview test, based on an American health care worker risk assessment scale project (HCWRAS) (Jackson MM, Lynch P, personal communication), which can be used to assess individual perceptions about potential risk of occupational infection. Participants were asked to select the five factors, from a list of fourteen, that they regarded as most important in potential bloodborne infection. The five factors were then placed in order of risk, indicating particularly the factors of highest and of lowest risk. Three nurses, one doctor, one psychologist, and one science researcher took part. There was no consensus as to a major risk factor (identified in the US project as prevalence of bloodbome pathogens in the population). Medium to low risk factors included, again without apparent consensus, condition of skin, frequency of performance of procedures with sharp items, emergency versus routine activity, amount of operator experience, or degree of blood exposure. This test is imprecise but as in the US HCWRAS study it seems that such an exercise involves considerable subjective assessment and the degree of risk posed by each factor is difficult for the individual to quantify; in the UK a "sharps" national code of
development into IQ type differences, even in infancy and early childhood.s Lately, a study of separated identical twins has fully substantiated traditional claims that IQ differences are of mainly genetic origin,6 the genetic influences presumably being mediated by lasting differences in nervous system functioning. Biological and environmental differences probably set up mental speed differences that lead to variations in general ability, tested IQ, and life chances. Even tested IQ differences, which develop towards the end of a complex causal chain, are demonstrably reliable, heritable, and predictive. How, then, can intelligence be so easily considered an illusion? C. R. BRAND P. G. CARYL I. J. DEARY V. EGAN H. C. PAGLIARI
Department of Psychology,
University of Edinburgh, Square, Edinburgh EH8 9JZ, UK
7 George
1. Schwartzman
AE, Gold D, Andres D, Arbuckle TY, Chaikelson J. Stability of intelligence: a 40-year follow-up. Can J Psychol 1987; 41: 244-56. 2. Hunter JE, Hunter RF. Validity and utility of alternative predictors of job performance. Psychol Bull 1984; 96: 72-98. 3. Blaha J, Wallbrown FH. Hierarchical factor structure of the WAIS-Revised. J Consul Clin Psychol 1982; 50: 652-60. 4. Kranzler JH, Jensen AR. Inspection time and intelligence: a meta-analysis. Intelligence 1989; 13: 329-47. 5. Bornstein MH, Sigman MD. Continuity in mental development from infancy. Child Dev 1986; 57: 251-74. 6. Bouchard TJ Jr, Lykken DT, McGue M, Segal NL, Tellegen A. Sources of human psychological differences: the Minnesota Study of twins reared apart. Science 1990; 250: 223-28.
So
long
SIR,-In your editorial of Feb 23 (p 460), you comment that "nobody dies of old age-that is to say, simply through the passage of time". Is this so? Many doctors will have had experience of elderly patients-frail, no doubt, but basically healthy and alert and quite active-who simply "died in their sleep". I have known three such patients, all women, two in their mid-80s and one in her early 90s. To me, people like that, rather than dying, simply stop living. So, the cause of death? To invoke a symptomless myocardial infarction in the absence of any evidence for it is clearly wrong. Admittedly, serial 5 fim sections of the whole of the brain and heart might reveal a cluster of cells that had undergone dissolution from the collapse, for some reason at some time, of some organelle. Then, after international agreement on the nature of the syndrome, the individual could be said to have died from this novel "disintegration xyz" rather than "old age". A search on this scale is impracticable so, in these circumstances, what explanation remains but old age? Your editorial refers later to a "fundamental interference with the
species ’clock’, which determines potential lifespan". I submit that it is precisely this fundamental interference, nature as yet unknown, that allows some fortunate people to die just of old age-and what a dignified entry that makes on a death certificate. Gowranes, Kinnaitd PH14 9QY, UK
WALLACE PARK
What do doctors know of statistics? SIR,-Dr Dodwell (Feb 16, p 432) raises an issue of concern when he asserts that "it is easier for a doctor to build up his personal statistical toolkit than for a statistician to attain sufficiently illuminating medical knowledge". Statisticians and doctors alike will recognise his satirical caricature of a consultation beween them. The question, however, is whether psychiatrists have devised more illuminating answers than those of the apocryphal statistician: if they have, they ought to let someone know, for statisticians have long sought the elixir that apparently resides in Dodwell’s toolkit. The ideal he recommends, exemplified by junior pyschiatric doctors receiving an education in research methodology, is worrying in the light of the research of Wulff et al.1 Medical participants in a course on postgraduate research methods scored a median of 4-0 correct answers out of 9 multiple choice questions relating to the understanding of elementary statistical expression (SD, SE, p < 0-05, p > 0 05, and r). These doctors would have found
less comfort from a senior colleague than from a hospital statistician for statistical advice-the median score dropped to 2-4 in a random sample of doctors, and the median was 2-1 among those who had qualified more than 15 years ago. The conclusion was that "the statistical knowledge of most doctors is so limited that they cannot be expected to draw the right conclusions from those statistical analyses which are found in papers in medical journals". Collaboration between doctors and statisticians has provided the scientific basis of contemporary medicine, and an increased knowledge of statistics among doctors can only improve the chances of fruitful communication. Before Dodwell advocates the scornful dismissal of expert advice in favour of the sparse contents of a personal toolkit he should consider something that Oscar Wilde actually did say: "The truth is seldom pure and never simple". Social Paediatric and Obstetric Research Unit, University of Glasgow, Glasgow G12 8RZ, UK
A. H. LEYLAND
C. W. PRITCHARD
1. Wulff HR, Anderson B, Brandenhoff P, Guttler F. What do doctors know about statistics? Stat Med 1987; 6: 3-10.
Assessment of risks and control in
occupational infection SIR,-Professor Scully and Dr Porter (Jan 19, p 178) refer to my general practice decontamination study’ as showing "poor" infection control in general practice. Rather, we reported a surprisingly large increase in autoclave ownership by UK general practitioners (49% of practices), compared with 8%2 and 25%3 of practices reported a year earlier. Many of our respondents indicated that they were planning to purchase an autoclave, and if our findings reflected a true increase in ownership over time then it is likely that more than three-quarters of general practices are now equipped with effective steriliser systems, as recommended by the British Medical Association (BA4A).’A follow-up study will be undertaken to reassess autoclave ownership and compliance with other infection control measures, such as glove use. Scully and Porter also raise the very important issue of hepatitis B vaccination for medical students. They report that as a matter of course dental students are vaccinated before qualification. There are about 8000 clinical medical students in the UK for whom vaccination should also be standard policy, as recommended by the BMA. S,6However, not all medical schools and hospital authorities accept this recommendation and educational programmes continue to be needed to raise awareness among clinical students, doctors, nurses, and other health care professionals. Risk assessment in clinical practice is an underestimated and vitally important matter. The risk of infection after needlestick injury with a sharp item contaminated with HIV-positive blood is substantial (1 in 200) and may relate to the amount of blood (and infectious virions) transferred during injury.’ Hepatitis B infection, however, is a far more likely risk (6-20%) after needlestick exposure, and hepatitis C risk has yet to be estimated but might be similar. I have piloted a simple interview test, based on an American health care worker risk assessment scale project (HCWRAS) (Jackson MM, Lynch P, personal communication), which can be used to assess individual perceptions about potential risk of occupational infection. Participants were asked to select the five factors, from a list of fourteen, that they regarded as most important in potential bloodborne infection. The five factors were then placed in order of risk, indicating particularly the factors of highest and of lowest risk. Three nurses, one doctor, one psychologist, and one science researcher took part. There was no consensus as to a major risk factor (identified in the US project as prevalence of bloodbome pathogens in the population). Medium to low risk factors included, again without apparent consensus, condition of skin, frequency of performance of procedures with sharp items, emergency versus routine activity, amount of operator experience, or degree of blood exposure. This test is imprecise but as in the US HCWRAS study it seems that such an exercise involves considerable subjective assessment and the degree of risk posed by each factor is difficult for the individual to quantify; in the UK a "sharps" national code of
