Risk of bias from inclusion of patients who already have diagnosis of or are undergoing treatment for depression in diagnostic accuracy studies of screening tools for depression: systematic reviewBMJ 2011; 343 doi: https://doi.org/10.1136/bmj.d4825 (Published 18 August 2011) Cite this as: BMJ 2011;343:d4825
- Brett D Thombs, associate professor of psychiatry1,
- Erin Arthurs, research assistant1,
- Ghassan El-Baalbaki, postdoctoral fellow1,
- Anna Meijer, doctoral student2,
- Roy C Ziegelstein, professor of medicine3,
- Russell J Steele, associate professor of mathematics and statistics4
- 1Lady Davis Institute for Medical Research, Jewish General Hospital and McGill University, Montreal, Quebec, Canada H3T 1E4
- 2Interdisciplinary Centre for Psychiatric Epidemiology, University Medical Centre Groningen, University of Groningen, 9713 GZ, Netherlands
- 3Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA
- 4Department of Mathematics and Statistics, McGill University, 805 Sherbrooke Ouest, Montreal, Quebec, H3A 2K6
- Correspondence to: B D Thombs
- Accepted 23 May 2011
Objectives To investigate the proportion of original studies included in systematic reviews and meta-analyses on the diagnostic accuracy of screening tools for depression that appropriately exclude patients who already have a diagnosis of or are receiving treatment for depression and to determine whether these systematic reviews and meta-analyses evaluate possible bias from the inclusion of such patients.
Design Systematic review.
Data sources Medline, PsycINFO, CINAHL, Embase, ISI, SCOPUS, and Cochrane databases were searched from 1 January 2005 to 29 October 2009.
Eligibility criteria for selecting studies Systematic reviews and meta-analyses in any language that reported on the diagnostic accuracy of screening tools for depression.
Results Only eight of 197 (4%) unique publications from 17 systematic reviews and meta-analyses specifically excluded patients who already had a diagnosis of or were receiving treatment for depression. No systematic reviews or meta-analyses commented on possible bias from the inclusion of such patients, even though 10 reviews used quality assessment tools with items to rate risk of bias from composition of the sample of patients.
Conclusions Studies of the accuracy of screening tools for depression rarely exclude patients who already have a diagnosis of or are receiving treatment for depression, a potential bias that is not evaluated in systematic reviews and meta-analyses. This could result in inflated estimates of accuracy on which clinical practice and preventive care guidelines are often based, a problem that takes on greater importance as the rate of diagnosed and treated depression in the population increases.
We thank Allison Leavens, Lisa R Jewett, and Brooke Levis, all of the Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada, for verification of referencing and study counts and proofreading the manuscript. They were not compensated for their contributions.
Contributors: BDT was responsible for the study concept and design, wrote the review protocol, supervised and carried out the data extraction, and drafted the manuscript with the input of the other authors. EA reviewed articles for inclusion, carried out the data extraction, contributed to the analysis, interpretation, and presentation of data, and conducted a critical revision of the manuscript. GE-B and AM participated in the design of the study, reviewed articles for inclusion, carried out the data extraction, and contributed a critical revision of the manuscript. RCZ contributed to the study design and contributed a critical revision of the manuscript. RJS contributed to the study design and analysis and interpretation of the data and contributed a critical revision of the manuscript. All authors had full access to all of the data (including statistical reports and tables) and take responsibility for the integrity of the data and the accuracy of the data analysis. BDT is guarantor.
Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. BDT is supported by a New Investigator Award from the Canadian Institutes of Health Research and an Établissement de Jeunes Chercheurs award from the Fonds de la Recherche en Santé Québec. RCZ is supported by the National Center for Complementary and Alternative Medicine (grant No R24AT004641) and the Miller Family Scholar Program of the Johns Hopkins Center for Innovative Medicine. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Complementary and Alternative Medicine or the National Institutes of Health.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: Not required.
Data sharing: No additional data available.
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