Evaluating treatment effects in group sequential multivariate longitudinal studies with covariate adjustment

Neal O. Jeffries, James F. Troendle and Nancy L. Geller

Biometrics, 2023, vol. 79, issue 2, 1496-1506

Abstract: Jeffries et al. (2018) investigated testing for a treatment difference in the setting of a randomized clinical trial with a single outcome measured longitudinally over a series of common follow‐up times while adjusting for covariates. That paper examined the null hypothesis of no difference at any follow‐up time versus the alternative of a difference for at least one follow‐up time. We extend those results here by considering multivariate outcome measurements, where each individual outcome is examined at common follow‐up times. We consider the case where there is interest in first testing for a treatment difference in a global function of the outcomes (e.g., weighted average or sum) with subsequent interest in examining the individual outcomes, should the global function show a treatment difference. Testing is conducted for each follow‐up time and may be performed in the setting of a group sequential trial. Testing procedures are developed to determine follow‐up times for which a global treatment difference exists and which individual combinations of outcome and follow‐up time show evidence of a difference while controlling for multiplicity in outcomes, follow‐up, and interim analyses. These approaches are examined in a study evaluating the effects of tissue plasminogen activator on longitudinally obtained stroke severity measurements.

Date: 2023
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