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Table 3 Comparison of ITT to PP outcomes in terms of ARR

From: Intention-to-treat analysis may be more conservative than per protocol analysis in antibiotic non-inferiority trials: a systematic review

  PP Median (IQR) ITT Median (IQR) Difference ITT – PP Median (IQR) Wilcoxon signed-rank test p-value PP analysis is more conservative N (%)
Point estimate −0.2 (−2.6, 2.2) 0.04 (− 2.6, 2.6) − 0.01 (− 1.6, 1.9) 0.7025 81 (49.4%)
CI width 12.4 (9.7, 16.6) 13.3 (11.2, 17.5) 0.9 (−0.4, 2.0) < 0.0001 58 (35.4%)
Lower CI limit −6.9 (− 10.0, −4.0) −7.5 (− 10.3, −4.7) −0.5 (− 1.8, 1.2) 0.0402 72 (43.9%)
  1. A positive value for the difference in CI width indicates less precise estimation of the ARR with ITT analysis. A negative difference for the lower CI limit signifies that the PP lower CI limit lies above the ITT CI limit, so ITT analysis has a more conservative result
  2. ARR Absolute risk reduction, CI Confidence interval, IQR Interquartile range, ITT Intention-to-treat, PP Per-protocol