Misconceptions About the Direction of Bias From Nondifferential Misclassification

Measurement error is pervasive in epidemiologic research. Epidemiologists often assume that mismeasurement of study variables is nondifferential with respect to other analytical variables and then rely on the heuristic that nondifferential misclassification will bias estimates towards the null. However, there are many exceptions to the heuristic for which bias towards the null cannot be assumed. In this paper, we compile and characterize 7 exceptions to this rule and encourage analysts to take a more critical and nuanced approach to evaluating and discussing bias from nondifferential mismeasurement.

Automated summary

Measurement error is common in epidemiologic research, and it is often assumed that nondifferential misclassification biases estimates towards the null. However, there are exceptions to this assumption, and a more critical and nuanced approach is needed to evaluate and discuss bias from nondifferential mismeasurement.