Bias control in cohort studies can be achieved by which approach?

• A. Loss to follow-up
• B. Improved per diem funding
• C. Avoiding registries
• D. Rigorous registries; detailed protocols; multivariate analysis

Answer: (D)

Bias control in cohort studies hinges on robust data collection, clear procedures, and careful analysis to minimize distortions in the measured associations. A well-maintained registry system provides comprehensive exposure and outcome information for all participants, which reduces information bias and issues related to incomplete follow-up. Detailed protocols ensure that data are collected the same way across sites and over time, limiting measurement error and misclassification. Multivariate analysis then allows adjustment for potential confounders, helping to isolate the true effect of the exposure from other factors that could distort the association.

Together, these elements address multiple bias pathways—information bias, selection or follow-up bias, and confounding—making findings more reliable. Other options fail to tackle bias in a comprehensive way: improving funding alone doesn’t ensure data quality or consistent collection; loss to follow-up by itself doesn’t correct data accuracy or confounding; avoiding registries removes a structured source of high-quality data.