In a randomised controlled trial, the concept of 'intention-to-treat' analysis is used primarily to:

• A Increase statistical power by excluding protocol violators
• B Preserve the benefits of randomisation and prevent attrition bias ✓
• C Estimate the efficacy of the drug in fully compliant patients
• D Eliminate confounding from baseline characteristics

Explanation

Intention-to-treat (ITT) analysis includes all randomised participants in the group to which they were originally allocated, regardless of protocol deviations, non-adherence, or withdrawal. This preserves the prognostic balance created by randomisation and prevents attrition bias (systematic dropout). Per-protocol analysis estimates efficacy in compliant patients (option C) but is susceptible to selection bias. ITT does not increase power — it typically reduces it somewhat. Randomisation itself eliminates confounding; ITT preserves that randomisation.

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

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Written and medically reviewed by the StethoPrep medical team.