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      The impact of consent on observational research: a comparison of outcomes from consenters and non consenters to an observational study

      , 1 , 1

      BMC Medical Research Methodology

      BioMed Central

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          Public health benefits from research often rely on the use of data from personal medical records. When neither patient consent nor anonymisation is possible, the case for accessing such records for research purposes depends on an assessment of the probabilities of public benefit and individual harm.


          In the late 1990s, we carried out an observational study which compared the care given to affluent and deprived women with breast cancer. Patient consent was not required at that time for review of medical records, but was obtained later in the process prior to participation in the questionnaire study. We have re-analysed our original results to compare the whole sample with those who later provided consent.


          Two important findings emerged from the re-analysis of our data which if presented initially would have resulted in insufficient and inaccurate reporting. Firstly, the reduced dataset contains no information about women presenting with locally advanced or metastatic cancer and we would have been unable to demonstrate one of our initial key findings: namely a larger number of such women in the deprived group. Secondly, our re-analysis of the consented women shows that significantly more women from deprived areas (51 v 31%, p = 0.018) received radiotherapy compared to women from more affluent areas. Previously published data from the entire sample demonstrated no difference in radiotherapy treatment between the affluent and deprived groups.


          The risk benefit assessment made regarding the use of medical records without consent should include the benefits of obtaining research evidence based on 100% of the population and the possibility of inappropriate or insufficient findings if research is confined to consented populations.

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          Most cited references 12

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          Patterns of consent in epidemiologic research: evidence from over 25,000 responders.

          Ethical guidelines in the United Kingdom require written consent from participants in epidemiologic studies for follow-up or review of medical records. This may cause bias in samples used for follow-up or medical record review. The authors analyzed data from seven general population surveys conducted in the United Kingdom (1996-2002), to which over 25,000 people responded. Associations of age, gender, and symptom under investigation with consent to follow-up and consent to review of medical records were examined. Consent to follow-up was approximately 75-95% among survey responders under age 50 years but fell among older people, particularly females. Consent to follow-up was also higher among responders who had the symptom under investigation (pooled odds ratio = 1.61, 95% confidence interval: 1.36, 1.92). Consent to review of medical records followed a similar pattern. Patterns of consent were relatively consistent and represented a high proportion of responders. Males, younger people, and subjects reporting the symptom under investigation were more likely to give consent, and these groups may be overrepresented in follow-up samples or reviews of medical records. Although consent is high among responders, the additive effect of nonresponse and nonconsent can substantially reduce sample size and should be taken into account in epidemiologic study planning.
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            Public attitudes towards the use of primary care patient record data in medical research without consent: a qualitative study.

             J. Fay,  K Hood,  M Robling (2004)
            Recent legislative changes within the United Kingdom have stimulated professional debate about access to patient data within research. However, there is currently little awareness of public views about such research. The authors sought to explore attitudes of the public, and their lay representatives, towards the use of primary care medical record data for research when patient consent was not being sought. 49 members of the public and four non-medical members of local community health councils in South Wales, UK gave their views on the value and acceptability of three current research scenarios, each describing access to data without patient consent. Among focus group participants, awareness of research in primary care was low, and the appropriateness of general practitioners as researchers was questioned. There was general support for research but also concerns expressed about data collection without consent. These included lack of respect and patient control over the process. Unauthorised access to data by external agencies was a common fear. Current data collection practices, including population based disease registers elicited much anxiety. The key informants were equally critical of the scenarios and generally less accepting. This exploratory study has highlighted a number of areas of public concern when medical records are accessed for research without patient consent. Public acceptability regarding the use of medical records in research cannot simply be assumed. Further work is required to determine how widespread such views are and to inform those advising on confidentiality issues.
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              Potential effect of authorization bias on medical record research.

              To analyze the influence of recent changes in Minnesota statutes that generally require prior authorization for use of medical records for research from patients who received medical care after Jan. 1, 1997. In this Mayo Clinic Institutional Review Board-approved study, we obtained a stratified random sample of patients encountered at Mayo Clinic Rochester during the period 1994 through 1996 and estimated the proportion willing to provide the general authorization. On the basis of data from administrative files, we then compared demographic, diagnostic, and utilization characteristics for patients who provided authorization and those who did not. Overall, 3.2% (95% confidence interval, 2.4 to 4.0%) of the study subjects declined authorization. If patients not responding to requests for authorization were also considered to have refused, the overall refusal rate would be 20.7% (95% confidence interval, 18.5 to 22.9%). Women were somewhat more likely to refuse authorization than were men (4.0% versus 2.4%; P = 0.067), and patients younger than 60 years were more likely to refuse than were older patients (5.4% versus 1.2%; P<0.001). Patients residing more than 120 miles from Rochester were much less likely to decline authorization than were local residents (2.1% versus 5.8%; P = 0.001). Patients with prior diagnoses that might be considered more sensitive such as mental disorders, infectious diseases, and reproductive problems also were more likely to refuse authorization. These data demonstrate that laws requiring written authorization for research use of the medical record could result in substantial biases in etiologic and outcome studies, the direction and magnitude of which may vary from topic to topic. Clinicians should be prepared to enter the discussion to help inform patients and legislators of the potential hazards of laws that restrict access to medical records for research purposes.

                Author and article information

                BMC Med Res Methodol
                BMC Medical Research Methodology
                BioMed Central
                3 April 2008
                : 8
                : 15
                [1 ]General Practice and Primary Care, Division of Community Based Sciences, Faculty of Medicine, University of Glasgow, 1 Horselethill Road, Glasgow, G12 9LX, UK
                Copyright © 2008 Macleod and Watt; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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