Assessment Bias

Abstract Assessment bias in a clinical trial arises if there is bias in the assessment of the outcome. It is also called ascertainment bias, diagnostic bias , or detection bias . A major cause of assessment bias is lack of blinding. Other problems relate to differential identification of harmless or false positive cases of disease, bias in assessment of disease‐specific mortality, the use of composite outcomes, competing risks, timing of the assessments, and bias in assessment of harms.