Searching the Biomedical Literature: Research Study Designs and Critical Appraisal

Peter W Callas

doi:10.29074/ascls.21.1.42

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Peter W Callas, PhD⇑
1. is research associate professor in the Department of Medical Biostatistics at the University of Vermont, Burlington VT

Address for correspondence: Peter W Callas PhD, research associate professor, Medical Biostatistics, University of Vermont College of Medicine, Hills Building, 105 Carrigan Drive, Burlington VT 05405. (802) 656-3195, (802) 656-0632 (fax). pcallas{at}uvm.edu.

Describe what is meant by “strength of evidence” when referring to research study designs.
Describe each of the following study designs: case report/case series, cross-sectional study, case-control study, cohort study (prospective and retrospective), and randomized controlled trials.
Discuss the strengths and weaknesses of each of the above study designs.
Define selection bias, recall bias, interviewer bias, and information bias.
Explain the major issues that should be considered when conducting a critical appraisal of a research study.

Extract

Two essential issues to consider when assessing the validity of research studies are the strengths and weaknesses of the study design and quality of methodology. This paper reviews study designs commonly used in clinical research, including case reports, cross-sectional studies, case-control studies, cohort studies, randomized controlled trials, reviews, and meta-analyses. It concludes with an outline for assessing study quality.

A search of the primary biomedical literature frequently brings up a number of research studies on the topic of interest. Much to the searcher's consternation, there will often be multiple studies that arrive at very different conclusions. Which is correct? Could two conflicting studies both be correct?

To answer these questions, the reader needs a sound basis on which to judge the quality of each study, for in reality, all published research studies are not equally valid. Some may be very strong, while others may have methodological weaknesses that render their findings questionable or even useless. In evaluating a research study, two essential issues must be considered: the particular study design used and its inherent strengths and weaknesses, and the quality of the methodology employed. This paper will review the various study designs commonly used in clinical research, and conclude with an outline for assessing the quality of individual studies.

STUDY DESIGNS Most papers encountered in the biomedical literature can be classified as one of three types: clinical research, basic science research, or non-research. Clinical research is any research involving human subjects. Basic science research consists of laboratory (“bench” or “test…

ABBREVIATIONS: AIDS = acquired immunodeficiency syndrome.

Describe what is meant by “strength of evidence” when referring to research study designs.
Describe each of the following study designs: case report/case series, cross-sectional study, case-control study, cohort study (prospective and retrospective), and randomized controlled trials.
Discuss the strengths and weaknesses of each of the above study designs.
Define selection bias, recall bias, interviewer bias, and information bias.
Explain the major issues that should be considered when conducting a critical appraisal of a research study.