What is information bias and provide an example in infectious disease epidemiology?

• A. Information bias is a systematic error in data collection; example: recall bias in self-reported exposure history.
• B. Information bias refers to random sampling errors.
• C. Information bias occurs when the sample is not representative due to nonresponse.
• D. Information bias is the same as selection bias.

Answer: (A)

Information bias is a systematic error in data collection or measurement that leads to misclassification of exposure or disease status. It distorts the observed association because the information you gather is biased, not just random.

A common infectious disease example is recall bias in case-control studies. When people with an infection (cases) are asked to report past exposures, they may remember and report exposures differently than those without infection (controls). For instance, cases might disproportionately recall having eaten a particular food or having been in contact with a known source, even if that exposure isn’t truly more common among cases. This differential misclassification of exposure creates a biased estimate of the association between that exposure and the disease.

This concept differs from random sampling errors, which are random fluctuations around the true value due to sampling variability, and from nonresponse bias, which stems from differences between respondents and nonrespondents (a form of selection bias). Saying information bias is the same as selection bias isn’t correct, because they are distinct types of bias.