RESEARCH DESIGN AND METHODS OF QUANTITATIVE SYNTHESIS OF MEDICAL EVIDENCE

Objective: To review the scientific principles, strengths, and limitat ions of research designs and methods of quantitative synthesis of medi cal evidence. Data Sources: We used MEDLINE to perform a systematic se arch for literature using the keywords research design, epidemiology, and biometry. Journals searched included six major journals in obstetr ics and gynecology and three in general medicine. These sources were s upplemented with texts and reviews from the general medical literature . Methods of Study Selection: We reviewed the publications identified by our search and evaluated critically the relevant reports. We summar ized objectives and scientific guidelines for the common research meth odologies and outlined their advantages and disadvantages. Tabulation, Integration, and Results: The standard of clinical research design is the randomized controlled trial (RCT), which, if performed with suffi cient methodologic rigor, is least likely to have serious biases. Coho rt, case-control, and cross-sectional studies are common observational studies used in reproductive health; such observational studies are m ore susceptible to biases that can distort the researcher's results an d conclusions. Descriptive studies such as case series and case report s are often interesting as clinical vignettes but have limited scienti fic merit. Methods for quantitative Synthesis of medical evidence, inc luding metaanalysis, decision analysis, and cost-effectiveness analysi s are being used with increased frequency in the reproductive health l iterature to summarize medical evidence. Conclusion: Various research methods have their own inherent advantages and disadvantages. An under standing of the scientific principles of these methods will enable the clinician to evaluate medical evidence critically. ((C) 1997 by The A merican College of Obstetricians and Gynecologists).