A case-control study recruits cases from tertiary hospital and controls from the same hospital for a different condition. Cases are more likely to have hypertension as a 'risk factor' for the outcome. However, hypertension independently leads to hospitalisation. This is:

• A Confounding by indication
• B Protopathic bias
• C Recall bias
• D Berkson's bias ✓

Explanation

Berkson's bias (hospital selection bias) occurs when both the disease under study and the putative risk factor are independently associated with hospitalisation, leading to a spurious association in hospital-based case-control studies. Controls selected from the same hospital may have conditions that are also associated with the exposure, distorting the OR. Confounding by indication occurs when the drug given for a disease is confounded with the disease's own risk. Protopathic bias is when treatment is given for early symptoms of the outcome being studied.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.