Comparing methods for handling missing cost and quality of life data in the Early Endovenous Ablation in Venous Ulceration trial.

objectivesThis study compares methods for handling missing data to conduct cost-effectiveness analysis in the context of a clinical study.

methodsPatients in the Early Endovenous Ablation in Venous Ulceration (EVRA) trial had between 1 year and 5.5 years (median 3 years) of follow-up under early or deferred endovenous ablation. This study compares complete-case-analysis (CCA), multiple imputation using linear regression (MILR) and using predictive mean matching (MIPMM), Bayesian parametric approach using the R package missingHE (BPA), repeated measures fixed effect (RMFE) and repeated measures mixed model (RMM). The outcomes were total mean costs and total mean quality-adjusted life years (QALYs) at different time horizons (1 year, 3 years and 5 years).

resultsAll methods found no statistically significant difference in cost at the 5% level in all time horizons, and all methods found statistically significantly greater mean QALY at year 1. By year 3, only BPA showed a statistically significant difference in QALY between treatments. Standard errors differed substantially between the methods employed.

conclusionCCA can be biased if data are MAR and is wasteful of the data. Hence the results for CCA are likely to be inaccurate. Other methods coincide in suggesting that early intervention is cost-effective at a threshold of £30,000 per QALY 1, 3 and 5 years. However, the variation in the results across the methods does generate some additional methodological uncertainty, underlining the importance of conducting sensitivity analyses using alternative approaches.