IJE Advance Access originally published online on April 30, 2007
International Journal of Epidemiology 2007 36(3):666-676; doi:10.1093/ije/dym018
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Tools for assessing quality and susceptibility to bias in observational studies in epidemiology: a systematic review and annotated bibliography
1Primary Care Genetics, General Practice and Primary Care Research Unit, University of Cambridge and Public Health Genetics Unit, Cambridge,
2Public Health Genetics Unit, Cambridge.
3MRC Biostatistics Unit, Cambridge and Public Health Genetics Unit, Cambridge, UK.
4Present address: PBSE, Hoffman-La Roche, Basel, Switzerland.
*Corresponding author and guarantor. Strangeways Research Labs, Worts Causeway, Cambridge CB1 8RN, UK. E-mail: simon.sanderson{at}srl.cam.ac.uk
| Abstract |
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Background Assessing quality and susceptibility to bias is essential when interpreting primary research and conducting systematic reviews and meta-analyses. Tools for assessing quality in clinical trials are well-described but much less attention has been given to similar tools for observational epidemiological studies.
Methods Tools were identified from a search of three electronic databases, bibliographies and an Internet search using Google®. Two reviewers extracted data using a pre-piloted extraction form and strict inclusion criteria. Tool content was evaluated for domains potentially related to bias and was informed by the STROBE guidelines for reporting observational epidemiological studies.
Results A total of 86 tools were reviewed, comprising 41 simple checklists, 12 checklists with additional summary judgements and 33 scales. The number of items ranged from 3 to 36 (mean 13.7). One-third of tools were designed for single use in a specific review and one-third for critical appraisal. Half of the tools provided development details, although most were proposed for future use in other contexts. Most tools included items for selection methods (92%), measurement of study variables (86%), design-specific sources of bias (86%), control of confounding (78%) and use of statistics (78%); only 4% addressed conflict of interest. The distribution and weighting of domains across tools was variable and inconsistent.
Conclusion A number of useful assessment tools have been identified by this report. Tools should be rigorously developed, evidence-based, valid, reliable and easy to use. There is a need to agree on critical elements for assessing susceptibility to bias in observational epidemiology and to develop appropriate evaluation tools.
Keywords Observational studies, epidemiological studies, quality, bias, checklist, scales
Accepted 29 January 2007
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