Rapid Responses to:
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involve the public
Rapid Responses: Rapid Responses published:
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Bias in data introduced by requiring consent
- Steven H Woolf, Stephen Rothemich, Robert Johnson, David Marsland (26 May 2002)
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Response to commentary on our article about patient consent for health surveillance.
- christopher m verity, Angus Nicoll (27 May 2002)
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Is medical surveillance an unmitigated blessing?
- Roger M. Goss (8 June 2002)
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Steven H Woolf, Professor of Family Practice Virginia Commonwealth University, Stephen Rothemich, Robert Johnson, David Marsland
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Verity and Nicoll are comprehensive in reviewing the potential impact that consent requirements could have on research, but they devote only one sentence to its impact on the validity of data. That is, requiring consent introduces a selection bias in study participants that, by skewing data, could misinform clinicians, policymakers, and the public about the effectiveness and safety of interventions. Verity and Nicoll touch on this point when they mention an American study, a 1999 report by Jacobsen et al., which "found that the requirement for consent led to selective exclusion of some patients and hence introduced bias." There has been at least one other American study of the same phenomenon, by our group, which also confirmed the introduction of a selection bias when primary care patients were asked to provide written consent for researchers to examine their medical records for health services research or to contact them for surveys (1). Those who gave consent differed significantly from those who did not give consent in terms of a number of demographic and health-related variables that have direct bearing on health outcomes and quality. The results of studies restricted to patients who give such consent are therefore potentially not generalizable to all persons receiving care. The requirement for consent thus pits two ethical duties against each other. One ethical duty is to safeguard the privacy of patients and the public. But consent requirements intended to protect this privacy run up against the ethical duty to ensure the safety and effectiveness of health care and public health interventions, which cannot be done accurately if consent requirements distort the data. Competing interests: None (1) Woolf SH, Rothemich SF, Johnson RE, Marsland DW. Selection bias from requiring patients to give consent to examine data for health services research. Arch Fam Pract 2000;9:1111-18. |
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christopher m verity, consultant paediatric neurologist Addenbrookes Hospital, Cambridge CB2 2QQ, Angus Nicoll
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Consent, confidentiality, and the threat to public health
surveillance
We agree with the comments that Dr Manning has made about involving the public – the need for doing so is one of the main points in our article (1). However we are concerned that Dr Manning did not take important practical issues into account before stating that “… the public will not accept waiving consent because “doctors cannot ‘get on round’ to seeking it”. He states that “seeking consent should not be too onerous for individual doctors” and recommends that doctors “give the consent process reasonable priority among their other commitments”. This implies that a bit more effort on the part of practising clinicians would make the problem go away. Dr Manning’s comments allow us to voice our main fear - that doctors, legislators, politicians and others involved in the debate about confidentiality will take the same deceptively simple view. We have not included patients or parents in that list as we believe that, when properly informed about the need, they accept the confidential transfer of clinical information between health professionals for public health purposes. The reasons for this belief are based on our experiences with parents, our discussions with parent support organisations and, incidentally, also appear in Dr Manning’s commentary. We have given examples of the worrying drop in reporting rates when it becomes necessary to obtain prior consent before sharing information about patients for public health purposes (1). We know that these falls in response do not occur merely because doctors do not make sufficient effort. They are due to substantial practical difficulties. Consider the reporting of infectious diseases. Millions of specimens are taken each year from patients for laboratory processing. Only a small proportion of these will turn out to be positive and need to be reported centrally for public health reasons. It would be pointlessly bureaucratic to obtain individual consent for transfer of positive results when these specimens are initially taken. However, when important positive results are obtained there is often the need to report quickly, perhaps in the context of a developing outbreak (2). It would be a slow and unreliable process if the laboratory then had to get back to the relevant patient via the individual clinician in order to get consent for transfer of the laboratory result, or for further study of the relevant microbiological isolate. Inevitably public health measures would be considerably delayed. Dr Manning argues that obtaining prior consent might be appropriate for smaller studies, such as of rare childhood diseases. However there are considerable practical problems here, too. The monthly surveillance card that the British Paediatric Surveillance Unit sends to over two thousand UK consultant paediatricians has up to a dozen different conditions on it at any time, and these conditions change over time. The individual paediatrician may report only one or two cases each year and some have no cases to report at all. Reporting is retrospective, the arrival of the card usually reminding paediatricians about the conditions that are currently being studied. They cannot reasonably be expected to remember exactly what is on the card each month. Therefore they are not usually able to ask parents for consent to transfer information at the time that the child is seen in the clinic or on the ward. Paediatricians having to obtain consent for surveillance studies would therefore have to contact the parents at some time after seeing their child. This would mean obtaining addresses and/or phone numbers. It would probably not be acceptable to make a phone call and ask for permission to transfer information relevant to a particular study. Written information would have to be sent to the parents. They would need time to consider this, ask questions and consider the replies before deciding to give written consent. When this process is considered in detail it becomes clear why response rates would drop if there were always a need to obtain prior consent. This is why we assert that such a need would seriously damage health surveillance. We would like to re-emphasise that any data that are transferred for public health reasons should only be seen by health professionals and should be dealt with in strict confidence. Studies of child health via the British Paediatric Surveillance Unit only rarely need to collect information sufficient to identify the individual patient. However, as we describe, occasional studies cannot be effectively carried out without transferring the patient’s name or other patient identifying information (1,3). We argue that this should occur only if there is an important public health need to carry out the study. Such identifying information will only be seen by the relevant surveillance team, would be kept confidentially and would be destroyed after it had fulfilled its function. Those who undertake such work need to produce accessible and clear explanatory information for patients and parents who wish to know, telling them what happens, why it is done and what checks and balances are in place (1). We hope that our article and the response to it will stimulate debate that will inform the public, health professionals and others involved in these important issues of confidentiality and consent. We think that more information should be available about the procedures that are in place to protect general health. We believe that one of the best public health systems in the world is under threat and we want as many people as possible to understand the reasons for our concern so that steps can be taken to protect health surveillance. 1. C Verity, A Nicoll, Consent, confidentiality, and the threat to public health surveillance. BMJ 2002;324:1210-1213 2. D Killalea L R Ward, D Roberts, J de Louvois, F Sufi, J M Stuart, et al International epidemiological and microbiological study of outbreak of Salmonella agona infection from a ready to eat savoury snack--I: England and Wales and the United States BMJ 1996;313:1105-1107. 3. C Verity, A Nicoll, Consent, confidentiality, and the threat to public health surveillance. BMJ 2002;324:1210-1213 (web insert :- http://bmj.com/cgi/content/full/324/7347/1210/DC1) |
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Roger M. Goss, Director Patient Concern
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Editor – Verity and Nicoll repeatedly assert the value of surveillance in protecting health. (1) They also advocate educating, rather than informing the public on this subject. How odd then that they fail to give any clear, concise or specific explanation of how “big brother” practices benefit those “spied” upon. Presumably they assume the benefits of breaking doctor/patient confidences and undermining trust are self-evident and unarguable. Perhaps those who provide the information in the course of medical care should decide the balance between the potential advantages of surveillance and what is acceptable or unacceptable intrusion on personal privacy. Roger M. Goss
(1) Verity C. and Nicoll A. Consent, confidentiality, and the threat to public health surveillance: BMJ 2002; 324: 1210-1213 (18 May) |
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