A randomised controlled trial of a new drug uses allocation concealment but fails to blind participants or outcome assessors. The most important consequence of this specific methodological gap is:
- A Performance bias and detection bias after randomisation ✓
- B Selection bias at the point of randomisation
- C Attrition bias due to unequal dropout
- D Reporting bias from selective outcome publication
Correct answer: A. Performance bias and detection bias after randomisation
Explanation
Allocation concealment prevents selection bias at the point of randomisation (investigators cannot foresee the next assignment). However, once allocation is known, the absence of blinding allows performance bias (differential care) and detection bias (systematic differences in outcome assessment). These are distinct risks from allocation concealment. Attrition bias depends on differential dropout, and reporting bias relates to publication or selective reporting of outcomes — neither is directly caused by lack of blinding.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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