In a randomized controlled trial, the primary outcome is measured at the end of the study period. Which of the following best describes the principle of 'intention-to-treat' (ITT) analysis?

Explanation

## Intention-to-Treat (ITT) Analysis **Key Point:** ITT analysis includes ALL randomized participants in their assigned groups, irrespective of whether they received, completed, or adhered to the assigned intervention. This preserves the benefits of randomization and reflects real-world effectiveness. ### Why ITT Matters **High-Yield:** ITT is the gold standard for RCT analysis because it: - Maintains the integrity of randomization - Prevents bias from differential dropout or non-adherence - Reflects pragmatic effectiveness (not just efficacy under ideal conditions) - Reduces selection bias that would arise if only compliant participants were analyzed ### ITT vs. Per-Protocol Analysis | Aspect | ITT | Per-Protocol | |--------|-----|-------------| | **Population** | All randomized participants | Only those who completed protocol | | **Bias Risk** | Lower (preserves randomization) | Higher (introduces selection bias) | | **Effect Size** | Conservative (tends to underestimate) | Inflated (overestimates efficacy) | | **Use in RCTs** | Primary analysis (mandatory) | Secondary/sensitivity analysis only | **Clinical Pearl:** ITT analysis may show smaller treatment effects than per-protocol analysis because it includes non-responders and those who didn't complete treatment—but this is the honest, unbiased estimate of real-world benefit. **Mnemonic:** **I-T-T = Include-Them-All** — all randomized participants stay in their assigned group for analysis, no matter what happened after randomization. [cite:Park 26e Ch 8]