Differential vs nondifferential outcome misclassification: which statement is correct?

• A. Differential outcome misclassification occurs when outcome assessment accuracy differs by exposure status.
• B. Nondifferential outcome misclassification occurs when accuracy differs by exposure status.
• C. Differential outcome misclassification occurs when outcomes are measured without regard to exposure.
• D. Outcome misclassification has no impact on bias.

Answer: (A)

Differential outcome misclassification happens when the accuracy of determining the outcome depends on the exposure status. In other words, the misclassification rates (or the sensitivity and specificity of outcome assessment) differ between exposed and unexposed groups. This difference can distort the observed association in any direction, making the measure of association biased in unpredictable ways.

That makes the statement stating this idea correct. By contrast, nondifferential misclassification means the outcome assessment accuracy is the same across exposure groups, not different. The idea that differential misclassification occurs when outcomes are measured without regard to exposure describes nondifferential misclassification, not differential. And saying there is no impact on bias is false—misclassification of outcomes can bias results.