In a randomized controlled trial, 15% of patients assigned to Drug X stopped taking it due to side effects and switched to standard care, yet the final analysis still classified them in the Drug X arm. This analytical approach was chosen primarily because it:

• A Increases the measured efficacy of Drug X
• B Preserves the prognostic balance achieved by randomization and reflects real-world effectiveness ✓
• C Eliminates the need for blinding of outcome assessment
• D Reduces the required sample size of the trial

Explanation

Intention-to-treat analysis keeps every randomized participant in the arm to which they were allocated, irrespective of adherence. Randomization distributes both known and unknown prognostic factors equally only at allocation; removing non-adherers destroys this balance and reintroduces selection bias, usually inflating apparent efficacy. ITT therefore answers the pragmatic question of whether a policy of prescribing the drug works in practice. It neither reduces sample size needs nor replaces blinding, and per-protocol analysis, not ITT, is the approach that tends to exaggerate efficacy.

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

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Written and medically reviewed by the StethoPrep medical team.