In a randomized trial of a new oral hypoglycaemic agent versus placebo, 15 percent of patients assigned to the drug stopped taking it after week 4. At 52 weeks, the investigators analyse every patient in the group to which they were originally randomized, counting events as they occurred. The main purpose of this approach is to:
- A Maximize the estimated treatment effect by removing non-adherent patients
- B Preserve the benefits of randomization and reflect real-world effectiveness ✓
- C Increase statistical power by reducing between-group variability
- D Adjust for confounding introduced by differential adherence
Correct answer: B. Preserve the benefits of randomization and reflect real-world effectiveness
Explanation
Intention-to-treat analysis retains all randomized patients in their original groups regardless of adherence, preserving the balance in baseline characteristics achieved by randomization and guarding against attrition bias. It also answers the practical question of whether the policy of prescribing the drug works in real conditions, including imperfect compliance. Per-protocol analysis, which excludes non-adherent patients, tends to inflate efficacy estimates and sacrifices the protection of randomization.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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