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False positives and negatives in routine testing for drugs of abuse
Folk medicine and
psychiatry
SIR-Jadhav’s commentary (April 1, p 808) starts with the example of a young Hindu male possessed by a ghost who, after a series of unsuccessful consultations with exorcists, is finally treated with antipsychotic drugs. Jadhav is concerned that phenomena integral to cultures of developing countries, and usually thought to help people cope with everyday life, are reduced by western psychiatry to mere mental conditions.
Although it is important to draw attention to this issue, we feel that three further points should be highlighted. First, many westerners themselves report what psychiatrists might diagnose as psychotic phenomena, while never presenting themselves for treatment-39% of college students report hearing their own thoughts spoken aloud and 5% have conversations with the voices,’ and 10-25% of the general population have had hallucinatory experiences at least once in their lifetimeIn other words there are many people who develop non-medical explanations for such occurrences, that might otherwise be classified as mental illness, but share the same wider culture as modern psychiatry. Second, doctors often believe a medical model approach is than a folk model; for example, it now seems that symptoms attributed to witchcraft by the medieval folk model, can now be explained as ergot poisoning due to fungal infection of rye in bread.; So could modern medicine have saved the lives of the 500 witches burnt in Geneva during 1515’-an event resulting from a folk interpretation of unusual behaviour? Third, we recognise that modern medicine has itself evolved so as to look back on previous medical practices with regret. Since the dopamine hypothesis of psychosis will in all probability be viewed by future generations of doctors as the late twentieth century version of witchcraft, we are anxious not to replace confidence in our treatment methods with arrogance.
more
Sarah
helpful
Knight, Amanda Perry, *Rajendra
Croydon Health Authority, Westways,
West
Persaud
Croydon, Surrey CR9 2RR, UK
belief system that is based upon a particular view of rational man hope to assess someone for whom such a worldview is completely alien? The result of this uncertainty on my rural practice has been a reappraisal of the understanding and role of traditional healers in the treatment of mental illness. They are quite often in a much better position to empathise and explain, and have the time to undertake therapy than the doctor in a busy rural hospital. This appreciation of the values of traditional healers has allowed us to start a dialogue with them on an equal footing, and to establish a mutual understanding which reaps the benefits of both paradigms.
Mickey Chopra Hlabisa Hospital, Hlabisa Rural Clinical Research Unit, Hlabisa 3937, Kwazulu, Natal, South Africa
1
2
3
4
2
3 4
Posey TB, Losch ME. Auditory hallucinations of hearing voices in normal subjects. Imagination, Cognition and Personality 1983; 2:
375
99-113 Slade PD, Bentall RP. Sensory deception: towards a scientific analysis of hallucinations. London: Croom Helm, 1988. Blakemore C. Mechanics of the mind. London: Cambridge University Press, 1977: 173. Leach E. Culture and reality Pychol Med 1978; 8: 555-64.
SiR-William Waldegrave, being well versed in Kuhnian ideas, would surely recognise that the nosology and therapy of western psychiatry is a particular paradigm rooted in western ideas and culture. Consultations with rural Zulu patients very quickly brings home the inappropriateness of many western psychiatric notions in other cultural settings. In an environment where "... reality consists in the relations not of men to things, but of men with other men, and of all men with spirits",’ not only am I ill equipped to discern the good and bad ghosts but also their mere presence can be the sign of a healthy mental state. In other words, both the content and form of mental illness is culturally determined. Therefore Jadhav is correct to point out the dubious credentials of western psychiatry for ghostbusting in other cultures and settings. However, if this were so, the validity of western psychiatric tools and categories as used, for instance, in the WHOs influential international pilot study of schizophreniamust be seriously questioned. Doubt is also cast on the validity of the persistent finding of higher levels of schizophrenia in people from the West Indies residing in the UK.’ How can a 1510
Med 1898; 18: 643-47. Harries A, Cullinan T. Herbis et orbis. the dangers of traditional eye medicines. Lancet 1994; 344: 1588.
positives and negatives in routine testing for drugs of abuse False
SIR-Notarianni and colleagues (April 29, p 1115) raise several issues relating to the testing of prisoners in England and Wales for drugs of abuse. Their point is well made about potential interference, by deliberate sample adulteration, in the immunochemical screening methods used to test for many misused drugs. Nevertheless, gas chromatography-mass spectroscopy (GC-MS) should not necessarily be the only method used for such analyses, even in circumstances in which there is a high true positive rate on
1
Lambo A. Traditional African cultures and western psychiatry, cited in: Fernando S. Race and culture in psychiatry. London: Croom Helm, 1988: 159. World Health Organization. Schizophrenia: an international follow-up study. London: Wiley, 1979. Harrison G, Owens D, Holton A, Neilson D, Boot D. A prospective study of severe mental disorder in Afro-Carribean patients. Psychol
testing.
GC-MS is expensive and cannot provide the instant screening result at sample collection, that an immunochemical screening test can. Even if the results of an immunochemical screening test have less than perfect specificity and sensitivity, this drawback is offset by the advantage of having a reasonably reliable result in a few minutes. Obviously, such results have to be interpreted in the light of knowledge of the assay’s performance characteristics. Although there are issues of privacy inherent in the collection of an unadulterated sample, it is arguable that reduction of supervision in the collection of urine samples in prison would increase the probability that some sample donors would use strategies, such as sample substitution, intended to defeat the object of the screening procedure. If the screening of prisoners for misused drugs is effective, the proportion of positive results can be expected to fall and, where the prevalence of positive results is low, then a testing protocol that involves an initial immunochemical screen followed by GC-MS confirmation will be cheaper than one that involves only GC-MS analysis of all samples. The legislative authority that allows the testing of prisoners for misused drugs is, in fact, quite limited. !,2 Authorisation for the collection of samples can be given only by the governor or director of a prison to ascertain whether the prisoner has a controlled drug, as defined in the Misuse of Drugs Act 1971, in his body. Many substances that might be misused by prisoners, such as fuel gases, solvents, alcohol, and anabolic steroids, are not defined in law as
controlled drugs and consequently
excluded from the
are
process, to the detriment of any deterrent effect of the policy. The legislation restricts the samples that can be obtained to urine and others, but not intimate samplessuch samples being defined in section V of the Police and Criminal Evidence Act 1984 (as amended) as "blood, semen or any other tissue fluid, urine, saliva or pubic hair". The
testing
Act goes on to define non-intimate samples as saliva and hair other than pubic hair. Thus, the legislation restricts sampling to the collection of urine, hair, and saliva. The collection of blood samples for drug screening is excluded. A R W Forrest Department of Clinical Chemistry, Royal Hallamshire Hospital, Sheffield S10 2JF, UK
1 2 3
Criminal Justice and Public Order Act 1994: Prison Act 1952: s 16 (as amended). Criminal Justice and Public Order Act 1994:
Basic
versus
applied
s
151.
s
58.
research
SiR-In your May 13 editorial you discuss the need for increased collaboration with the pharmaceutical industry in funding all aspects of medical research. You highlighted an interesting collaborative research project on tuberculosis sponsored by Glaxo. You cite Professor John Polanyi, who is purported to have said in a recent lecture: "it is essential to prevent the applied sector from setting the agenda for the basic". Although the risks of this happening are easily seen, it is rarely stated that there are risks inherent in the converse situation. No level of investigation is inherently better than any other. Developments and improvements in our knowledge come not from a predictable pathway from basic mechanisms through to clinical diseases and public health measures, but rather from a multipronged attack on areas of ignorance. When it comes to understanding the details of and their disease mechanisms most appropriate in of individual both terms management, patients and in population strategies, the correct answer arises as a film would develop, with gradual clarity developing in all areas simultaneously. It is rather like an enormous jigsaw puzzle with hundreds of individual participants completing sections of the puzzle at the same time, with some who are expert at visualising the whole picture. Why then do we emphasise the risk of applied research dominating when in fact there is a similar risk that basic research could be perceived as giving a purer or more definitive answer? We have learnt many times in the past that oversimplistic explanations based on the perception that we understand the basic processes can lead to errors that can set back eventual knowledge for decades or longer. We cannot hope to understand all the factors in complex integration by studying the individual building blocks and extrapolating upwards. Research in biomathematics and other related specialties has shown that complex systems behave in unpredictable ways, because of the enormous number of chance events that can interact in such a way as to develop apparently chaotic behaviour. Although it is obviously of immense interest to study mechanisms at the most basic level possible, it is also essential that we study the system at all levels to understand the whole. I would, therefore, warn that it is also crucial to prevent the basic sector from setting the agenda for the applied, since the researchers do not have the training, information, or expertise so to do. In biology research, the latest popular topic for basic investigation is molecular processes, and there is a fairly widely held belief that by understanding these processes we will be able to deduce the functioning of an intact organism in health or disease. Unfortunately, like all
basic research, this assumption is oversimplistic, and unless we ensure adequate funding and support for research for all types of investigation, we will waste valuable time and resources.
previous
Andrew J S Coats National Heart and
Lung Institute,
London SW3 6LY, UK
European schools of public health SiR-de Leeuw’s report (May 6, p 1158) is a good summary of the organisational structures of the European schools of public health. But it is not quite clear what is behind these structures and the understanding of public health that they reproduce. The classic model of schools of public health, as a department of medical schools, reproduces a medicalised version of public health that constrains their development. Public health is not a branch of medicine, but medicine is a part of public health. The other traditional location of schools of public health-ie, in the state administrationalso impoverishes these schools since they are not part of an academic environment that can stimulate and enrich them. These limitations have stimulated a new development of independent but academic-based schools of public health. Although this is an important step, it is still insufficient. Public health schools should be part of public policy in which the studies of public health should be fully immersed in the understanding of the sociopolitical and economic forces that shape the nature of the public’s health. Very few are.
Vicente Navarro School of Hygiene and Public Health, Department of Health Johns Hopkins University, Baltimore, MD 21205, USA
Loss to
Policy and Management,
follow-up: does it matter?
SiR-Vigorous attempts should be made to trace any patients who fail to attend a follow-up clinic, but inevitably not all will be found, and such patients are deemed lost to follow-up. In survival analyses they are assumed to have the aggregate outcome as those who continue to be assessed. This assumption should be questioned’°2 since patients with follow-up appointments who do not attend may well be seeking medical attention elsewhere.3 In their study of 100 hip replacements, Dorey and Amstutz4 suggested that these fears are ungrounded. They originally followed 55% of their patients, but after a second attempt 90% were located. The survival rates were the same in both attempts and they therefore concluded that loss to follow-up was not important. This conclusion has been challenged on the grounds that patients who are especially unwilling to return for follow-up will be included in the last 10%.5 We have attempted to identify the loss to follow-up bias in a study of 2268 patients who had a total hip replacement between 1967 and 1989. The patients were reviewed clinically and radiographically 6 months after operation and then at 1 year, and every 2 years thereafter-some until 16 years after the initial operation. During the course of the same
*Lost to follow-up minus matched scores. Table: Differences in significance of outcome measures in patients lost to follow-up versus matched patients who continued to attend 1511
psychiatry
SIR-Jadhav’s commentary (April 1, p 808) starts with the example of a young Hindu male possessed by a ghost who, after a series of unsuccessful consultations with exorcists, is finally treated with antipsychotic drugs. Jadhav is concerned that phenomena integral to cultures of developing countries, and usually thought to help people cope with everyday life, are reduced by western psychiatry to mere mental conditions.
Although it is important to draw attention to this issue, we feel that three further points should be highlighted. First, many westerners themselves report what psychiatrists might diagnose as psychotic phenomena, while never presenting themselves for treatment-39% of college students report hearing their own thoughts spoken aloud and 5% have conversations with the voices,’ and 10-25% of the general population have had hallucinatory experiences at least once in their lifetimeIn other words there are many people who develop non-medical explanations for such occurrences, that might otherwise be classified as mental illness, but share the same wider culture as modern psychiatry. Second, doctors often believe a medical model approach is than a folk model; for example, it now seems that symptoms attributed to witchcraft by the medieval folk model, can now be explained as ergot poisoning due to fungal infection of rye in bread.; So could modern medicine have saved the lives of the 500 witches burnt in Geneva during 1515’-an event resulting from a folk interpretation of unusual behaviour? Third, we recognise that modern medicine has itself evolved so as to look back on previous medical practices with regret. Since the dopamine hypothesis of psychosis will in all probability be viewed by future generations of doctors as the late twentieth century version of witchcraft, we are anxious not to replace confidence in our treatment methods with arrogance.
more
Sarah
helpful
Knight, Amanda Perry, *Rajendra
Croydon Health Authority, Westways,
West
Persaud
Croydon, Surrey CR9 2RR, UK
belief system that is based upon a particular view of rational man hope to assess someone for whom such a worldview is completely alien? The result of this uncertainty on my rural practice has been a reappraisal of the understanding and role of traditional healers in the treatment of mental illness. They are quite often in a much better position to empathise and explain, and have the time to undertake therapy than the doctor in a busy rural hospital. This appreciation of the values of traditional healers has allowed us to start a dialogue with them on an equal footing, and to establish a mutual understanding which reaps the benefits of both paradigms.
Mickey Chopra Hlabisa Hospital, Hlabisa Rural Clinical Research Unit, Hlabisa 3937, Kwazulu, Natal, South Africa
1
2
3
4
2
3 4
Posey TB, Losch ME. Auditory hallucinations of hearing voices in normal subjects. Imagination, Cognition and Personality 1983; 2:
375
99-113 Slade PD, Bentall RP. Sensory deception: towards a scientific analysis of hallucinations. London: Croom Helm, 1988. Blakemore C. Mechanics of the mind. London: Cambridge University Press, 1977: 173. Leach E. Culture and reality Pychol Med 1978; 8: 555-64.
SiR-William Waldegrave, being well versed in Kuhnian ideas, would surely recognise that the nosology and therapy of western psychiatry is a particular paradigm rooted in western ideas and culture. Consultations with rural Zulu patients very quickly brings home the inappropriateness of many western psychiatric notions in other cultural settings. In an environment where "... reality consists in the relations not of men to things, but of men with other men, and of all men with spirits",’ not only am I ill equipped to discern the good and bad ghosts but also their mere presence can be the sign of a healthy mental state. In other words, both the content and form of mental illness is culturally determined. Therefore Jadhav is correct to point out the dubious credentials of western psychiatry for ghostbusting in other cultures and settings. However, if this were so, the validity of western psychiatric tools and categories as used, for instance, in the WHOs influential international pilot study of schizophreniamust be seriously questioned. Doubt is also cast on the validity of the persistent finding of higher levels of schizophrenia in people from the West Indies residing in the UK.’ How can a 1510
Med 1898; 18: 643-47. Harries A, Cullinan T. Herbis et orbis. the dangers of traditional eye medicines. Lancet 1994; 344: 1588.
positives and negatives in routine testing for drugs of abuse False
SIR-Notarianni and colleagues (April 29, p 1115) raise several issues relating to the testing of prisoners in England and Wales for drugs of abuse. Their point is well made about potential interference, by deliberate sample adulteration, in the immunochemical screening methods used to test for many misused drugs. Nevertheless, gas chromatography-mass spectroscopy (GC-MS) should not necessarily be the only method used for such analyses, even in circumstances in which there is a high true positive rate on
1
Lambo A. Traditional African cultures and western psychiatry, cited in: Fernando S. Race and culture in psychiatry. London: Croom Helm, 1988: 159. World Health Organization. Schizophrenia: an international follow-up study. London: Wiley, 1979. Harrison G, Owens D, Holton A, Neilson D, Boot D. A prospective study of severe mental disorder in Afro-Carribean patients. Psychol
testing.
GC-MS is expensive and cannot provide the instant screening result at sample collection, that an immunochemical screening test can. Even if the results of an immunochemical screening test have less than perfect specificity and sensitivity, this drawback is offset by the advantage of having a reasonably reliable result in a few minutes. Obviously, such results have to be interpreted in the light of knowledge of the assay’s performance characteristics. Although there are issues of privacy inherent in the collection of an unadulterated sample, it is arguable that reduction of supervision in the collection of urine samples in prison would increase the probability that some sample donors would use strategies, such as sample substitution, intended to defeat the object of the screening procedure. If the screening of prisoners for misused drugs is effective, the proportion of positive results can be expected to fall and, where the prevalence of positive results is low, then a testing protocol that involves an initial immunochemical screen followed by GC-MS confirmation will be cheaper than one that involves only GC-MS analysis of all samples. The legislative authority that allows the testing of prisoners for misused drugs is, in fact, quite limited. !,2 Authorisation for the collection of samples can be given only by the governor or director of a prison to ascertain whether the prisoner has a controlled drug, as defined in the Misuse of Drugs Act 1971, in his body. Many substances that might be misused by prisoners, such as fuel gases, solvents, alcohol, and anabolic steroids, are not defined in law as
controlled drugs and consequently
excluded from the
are
process, to the detriment of any deterrent effect of the policy. The legislation restricts the samples that can be obtained to urine and others, but not intimate samplessuch samples being defined in section V of the Police and Criminal Evidence Act 1984 (as amended) as "blood, semen or any other tissue fluid, urine, saliva or pubic hair". The
testing
Act goes on to define non-intimate samples as saliva and hair other than pubic hair. Thus, the legislation restricts sampling to the collection of urine, hair, and saliva. The collection of blood samples for drug screening is excluded. A R W Forrest Department of Clinical Chemistry, Royal Hallamshire Hospital, Sheffield S10 2JF, UK
1 2 3
Criminal Justice and Public Order Act 1994: Prison Act 1952: s 16 (as amended). Criminal Justice and Public Order Act 1994:
Basic
versus
applied
s
151.
s
58.
research
SiR-In your May 13 editorial you discuss the need for increased collaboration with the pharmaceutical industry in funding all aspects of medical research. You highlighted an interesting collaborative research project on tuberculosis sponsored by Glaxo. You cite Professor John Polanyi, who is purported to have said in a recent lecture: "it is essential to prevent the applied sector from setting the agenda for the basic". Although the risks of this happening are easily seen, it is rarely stated that there are risks inherent in the converse situation. No level of investigation is inherently better than any other. Developments and improvements in our knowledge come not from a predictable pathway from basic mechanisms through to clinical diseases and public health measures, but rather from a multipronged attack on areas of ignorance. When it comes to understanding the details of and their disease mechanisms most appropriate in of individual both terms management, patients and in population strategies, the correct answer arises as a film would develop, with gradual clarity developing in all areas simultaneously. It is rather like an enormous jigsaw puzzle with hundreds of individual participants completing sections of the puzzle at the same time, with some who are expert at visualising the whole picture. Why then do we emphasise the risk of applied research dominating when in fact there is a similar risk that basic research could be perceived as giving a purer or more definitive answer? We have learnt many times in the past that oversimplistic explanations based on the perception that we understand the basic processes can lead to errors that can set back eventual knowledge for decades or longer. We cannot hope to understand all the factors in complex integration by studying the individual building blocks and extrapolating upwards. Research in biomathematics and other related specialties has shown that complex systems behave in unpredictable ways, because of the enormous number of chance events that can interact in such a way as to develop apparently chaotic behaviour. Although it is obviously of immense interest to study mechanisms at the most basic level possible, it is also essential that we study the system at all levels to understand the whole. I would, therefore, warn that it is also crucial to prevent the basic sector from setting the agenda for the applied, since the researchers do not have the training, information, or expertise so to do. In biology research, the latest popular topic for basic investigation is molecular processes, and there is a fairly widely held belief that by understanding these processes we will be able to deduce the functioning of an intact organism in health or disease. Unfortunately, like all
basic research, this assumption is oversimplistic, and unless we ensure adequate funding and support for research for all types of investigation, we will waste valuable time and resources.
previous
Andrew J S Coats National Heart and
Lung Institute,
London SW3 6LY, UK
European schools of public health SiR-de Leeuw’s report (May 6, p 1158) is a good summary of the organisational structures of the European schools of public health. But it is not quite clear what is behind these structures and the understanding of public health that they reproduce. The classic model of schools of public health, as a department of medical schools, reproduces a medicalised version of public health that constrains their development. Public health is not a branch of medicine, but medicine is a part of public health. The other traditional location of schools of public health-ie, in the state administrationalso impoverishes these schools since they are not part of an academic environment that can stimulate and enrich them. These limitations have stimulated a new development of independent but academic-based schools of public health. Although this is an important step, it is still insufficient. Public health schools should be part of public policy in which the studies of public health should be fully immersed in the understanding of the sociopolitical and economic forces that shape the nature of the public’s health. Very few are.
Vicente Navarro School of Hygiene and Public Health, Department of Health Johns Hopkins University, Baltimore, MD 21205, USA
Loss to
Policy and Management,
follow-up: does it matter?
SiR-Vigorous attempts should be made to trace any patients who fail to attend a follow-up clinic, but inevitably not all will be found, and such patients are deemed lost to follow-up. In survival analyses they are assumed to have the aggregate outcome as those who continue to be assessed. This assumption should be questioned’°2 since patients with follow-up appointments who do not attend may well be seeking medical attention elsewhere.3 In their study of 100 hip replacements, Dorey and Amstutz4 suggested that these fears are ungrounded. They originally followed 55% of their patients, but after a second attempt 90% were located. The survival rates were the same in both attempts and they therefore concluded that loss to follow-up was not important. This conclusion has been challenged on the grounds that patients who are especially unwilling to return for follow-up will be included in the last 10%.5 We have attempted to identify the loss to follow-up bias in a study of 2268 patients who had a total hip replacement between 1967 and 1989. The patients were reviewed clinically and radiographically 6 months after operation and then at 1 year, and every 2 years thereafter-some until 16 years after the initial operation. During the course of the same
*Lost to follow-up minus matched scores. Table: Differences in significance of outcome measures in patients lost to follow-up versus matched patients who continued to attend 1511