How to Detect and Handle Confounding Factors

Abstract

How to Detect and Handle Confounding Factors

Sirima Mongkolsomlit BSc, MSc Epidemiology*

Jayanton Patumanond MD, DTM&H, MSc Clin Trop Med, DSc Clinical Epidemiology**

Petch Rawdaree MD, MSc Epidemiology, DLSHTM***

* Faculty of Public Health, Thammasart University.

** Faculty of Medicine, Chiangmai University.

*** Department of Medicine, BMA Medical College and Vajira Hospital.

When a researcher investigates the association between an exposure of factors and an occurrence of outcome, there are other influencing factors to the test result so called "confounding factors". Confounding factors may cause indistinct or inaccurate results of the study. Since statistical analysis cannot clear out the effect of confounders which have not been collected or being unidentified, it is crucial for the researcher to identify and control the impact of these confounding factors. In order to collect all essential data including any potential confounding factors, a thorough literature review prior to conducting a research is the first and important step. If confounders are identified, there are many approaches to deal with confounders: by randomization, restriction, or matching in the research design or methodology process; or by stratification or multivariable analysis in the statistical analysis process.

Keywords: confounding factors, randomization, restriction, matching, stratification

Vajira Med J 2010 ; 54 : 223-235