Comparing different methods for analyzing hierarchical composite endpoints: two illustrative case studies with post-hoc analyses of the BALANCE and CAMERA2 randomized clinical trials

Abstract

Objectives: Hierarchical composite endpoints (HCEs) are increasingly being used in infectious disease research. In this paper, we illustrate different methods for analyzing HCEs in post-hoc analyses of the BALANCE and CAMERA2 clinical trials.

Methods: We constructed post-hoc HCEs for each trial by combining clinical efficacy and safety outcomes: (a) mortality, relapse of bacteremia, and antibiotic adverse events for BALANCE, and (b) mortality, primary treatment failure, infectious complications, and antibiotic adverse events for CAMERA2. For both trials, we additionally included length of stay (LOS) or duration of antibiotic treatment as tiebreakers after the primary HCE in separate analyses. We applied these analytic methods: (a) logistic regression using a binary composite outcome, (b) generalized pairwise comparisons using different outcome permutations, (c) Wilcoxon rank-sum approach for an ordinal outcome, (d) proportional odds model, and (e) probabilistic index model. We estimated the probabilistic index, win ratio, win odds, net treatment benefit, or odds ratio where possible using each method.

Results: For the BALANCE trial, all analyses of the primary HCE resulted in the same conclusion of no evidence of differences between treatment groups. Inclusion of LOS as a tiebreaker resulted in 7 of 11 analyses finding the 7-day treatment arm superior to the 14-day arm, while inclusion of antibiotic duration resulted in all analyses concluding superiority of the 7-day treatment arm. For the CAMERA2 trial, all analyses found no evidence of differences between the two treatment groups. For all analyses, there were only minor differences in estimates across different analytic methods.

Conclusions: In these post-hoc analyses, different methods for analyzing HCEs resulted in similar effect estimates and conclusions consistent with the primary analyses of the BALANCE and CAMERA2 trials. These analyses illustrate how different HCEs can be constructed and analyzed, and may be useful to other researchers in designing future studies that use HCEs.

Keywords: antibiotic duration; clinical trial; hierarchical composite endpoints; ordinal outcomes; outcomes; trial design.