J Korean Med Assoc.  2011 Oct;54(10):1006-1012.

A method to evaluate scientific evidence in clinical preventive medicine

• Lee J
• Park BJ

Abstract

Evaluation of scientific evidence in the medical literature is based on the research methodology, which can be the fundamental tool for medical professionals to improve their practice. Since analytic studies usually provide evidence for generating hypotheses and selecting appropriate research designs, this article aims to review the methods for evaluating the study quality in randomized controlled trials (RCTs), cohort studies, and case-control studies. Critical appraisal of systematic errors including selection bias, performance bias, attrition bias, detection bias, and publication bias are the essential elements of the evaluation. Clinical trials need to have an adequate description of sequence generation and allocation concealment, blinding for exposure measurement, completeness of follow-up and intention to treat analysis, and blinding for outcome evaluation. For cohort studies, like RCTs, appropriate control of confounding variables is needed to prevent selection bias, and blinding and completeness of follow-up are also very important. Matching of the case group to the control group, blinding of interviewers, and proper definition of the cases and controls are important to prevent bias in a case-control study. Since the process of critical appraisal depends on the quality of reporting, there have been efforts to improve the reporting quality of the medical literature. However, reporting all of the elements necessary to avoid bias does not automatically guarantee an exclusion of bias or the quality of a study; instead, what is important is the logical connection of the elements of a study and the eventual lucid expression of the elements.

Keyword

Randomized controlled trial; Cohort studies; Case-control studies; Bias; Critical appraisal

MeSH Terms

Bias (Epidemiology)
Case-Control Studies
Cohort Studies
Confounding Factors (Epidemiology)
Follow-Up Studies
Intention to Treat Analysis
Logic
Preventive Medicine
Publication Bias
Research Design
Selection Bias

Reference

1. Crombie IK. The pocket guide to critical appraisal: a handbook of healthcare professionals. 1996. London: BMJ Publishing Group;66.

2. Leon G. Epidemiology. 2004. 3rd ed. Pennsylvania: Saunders;335.

3. Ahn YO. Epidemiology: the principles and applications. 2005. 1st ed. Seoul: SNU Press;347.

4. Park BJ, editor. evidence-based healthcare. 2009. 1st ed. Seoul: Korea Medical Book;364.

5. Park BJ, Cho YK, Kim SA. Construction of the Korea elderly pharmacoepidemiologic cohort: drug utilization review of cephalosporins in geriatric inpatients. Pharmacoepidemiol Drug Saf. 2001. 10:487–492.

6. Bae JM, Koo HW, Jung KO, Park BJ. A cohort study on the association between psychotropics and hip fracture in Korean elderly women. J Korean Med Sci. 2002. 17:65–70.

7. Brookhart MA, Wang PS, Solomon DH, Schneeweiss S. Evaluating short-term drug effects using a physician-specific prescribing preference as an instrumental variable. Epidemiology. 2006. 17:268–275.

8. Robins JM, Hernan MA, Brumback B. Marginal structural models and causal inference in epidemiology. Epidemiology. 2000. 11:550–560.

9. Kleinbaum DG, Kupper LL, Morgenstern H. Epidemiologic research: principles and quantitative methods. 1982. Tokyo: ITP;529.

10. Yoon BW, Bae HJ, Hong KS, Lee SM, Park BJ, Yu KH, Han MK, Lee YS, Chung DK, Park JM, Jeong SW, Lee BC, Cho KH, Kim JS, Lee SH, Yoo KM. Acute Brain Bleeding Analysis (ABBA) Study Investigators. Phenylpropanolamine contained in cold remedies and risk of hemorrhagic stroke. Neurology. 2007. 68:146–149.

11. Schulz KF, Altman DG, Moher D. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. J Pharmacol Pharmacother. 2010. 1:100–107.

12. Von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP. Iniciativa STROBE. The strengthening the reporting of observational studies in epidemiology (STROBE) statement: guidelines for reporting observational studies. Rev Esp Salud Publica. 2008. 82:251–259.

13. Easterbrook PJ, Berlin JA, Gopalan R, Matthews DR. Publication bias in clinical research. Lancet. 1991. 337:867–872.