In a randomized trial of a new antidiabetic drug, 15% of patients assigned to the drug never take a single dose, yet the primary analysis includes them in the drug arm. This analytic approach was chosen primarily because it:

• A Increases the measured treatment effect
• B Eliminates loss to follow-up
• C Is required for regulatory approval of all drugs
• D Preserves the prognostic balance achieved by randomization ✓

Explanation

Intention-to-treat analysis retains every randomized participant in the originally assigned arm regardless of adherence. Patients who comply may differ systematically in prognosis from non-compliers, so excluding them breaks the balance created by randomization and reintroduces selection bias. ITT therefore estimates the effect of assigning treatment under real-world conditions. It does not inflate the effect estimate, it is not mandated for approval of every drug, and it does nothing about participants actually lost to follow-up.

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

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