Intention-to-treat analysis

ITT Analysis - Everyone Counts!

• Core Principle: All subjects are analyzed in the group they were randomized to, regardless of non-compliance, protocol deviation, or withdrawal.
  • 📌 As randomized, so analyzed.
• Benefit: Preserves the original randomization, preventing confounding and selection bias that can arise from post-randomization events.
• Interpretation: Estimates the effect of the treatment strategy as a whole, not just the treatment itself. This reflects real-world effectiveness where patient adherence varies.
• Result: Usually provides a more conservative (smaller) estimate of the treatment effect. It answers the question: "What is the effect of prescribing this drug?"

⭐ High-Yield: ITT analysis is considered the gold standard for RCTs because it avoids the effects of crossover and dropout, thus preserving the integrity of randomization.

ITT vs. Per‑Protocol - The Showdown

• A crucial decision in RCT analysis is choosing the patient population. This choice pits real-world applicability (effectiveness) against ideal-condition results (efficacy).

ITT Effects - Bias vs. Reality

• Core Principle: Analyzes all randomized patients in their original assigned groups, regardless of adherence, protocol deviation, or withdrawal. 📌 Include Them all in their Treatment group.
• Bias Mitigation:
  • Prevents attrition and crossover bias.
  • Maintains the integrity of randomization, ensuring baseline comparability between groups is preserved.
• Effect on Results:
  • Mirrors real-world clinical practice where patient adherence is imperfect.
  • Typically provides a more conservative (smaller) estimate of the treatment effect. The dilution from non-adherence pushes the result towards the null hypothesis (no effect).

⭐ ITT analysis is the gold standard for assessing pragmatic clinical effectiveness, as it preserves the prognostic balance created by randomization.

• "Once randomized, always analyzed" is the core principle of Intention-to-Treat (ITT) analysis.
• Data is analyzed based on the patient's original group assignment, irrespective of treatment adherence or withdrawal.
• ITT preserves the benefits of randomization, preventing selection bias and maintaining prognostic balance.
• It generally provides a more conservative but realistic estimate of a treatment's effect in a real-world setting.
• This approach reflects treatment effectiveness, while per-protocol analysis measures treatment efficacy.