Key result
Transporting trial results to a Medicare population yielded two-year mortality risk differences for dabigatran versus warfarin (-0.57%) closer to the null than nonexperimental methods (-1.9%).
Why the study?
Trial and nonexperimental results are often compared without accounting for study population differences, which trial transport methods can address.
Does dabigatran compared to warfarin reduce ischemic stroke, mortality, and gastrointestinal bleeding in older adults with atrial fibrillation?
Observational
Does dabigatran compared to warfarin reduce ischemic stroke, mortality, and gastrointestinal bleeding in older adults with atrial fibrillation?
Differences in study populations should be quantitatively considered when comparing trial with nonexperimental findings, as effect estimates for mortality and bleeding can vary significantly depending on the method used.
Transporting trial results attenuates mortality benefits versus nonexperimental estimates in Medicare patients; leaves open optimal methods for generalizing dabigatran findings.
Background: Results from trials and nonexperimental studies are often directly compared, with little attention paid to differences between study populations. When target and trial population data are available, accounting for these differences through transporting trial results to target populations of interest provides useful perspective. We aimed to compare two-year risk differences (RDs) for ischemic stroke, mortality, and gastrointestinal bleeding in older adults with atrial fibrillation initiating dabigatran and warfarin when using trial transport methods versus nonexperimental methods. Methods: We identified Medicare beneficiaries who initiated warfarin or dabigatran from a 20% nationwide sample. To transport treatment effects observed in the randomized evaluation of long-term anticoagulation trial, we applied inverse odds weights to standardize estimates to two Medicare target populations of interest, initiators of: (1) dabigatran and (2) warfarin. Separately, we conducted a nonexperimental study in the Medicare populations using standardized morbidity ratio weighting to control measured confounding. Results: Comparing dabigatran to warfarin, estimated two-year RDs for ischemic stroke were similar with trial transport and nonexperimental methods. However, two-year mortality RDs were closer to the null when using trial transport versus nonexperimental methods for the dabigatran target population (transported RD: −0.57%; nonexperimental RD: −1.9%). Estimated gastrointestinal bleeding RDs from trial transport (dabigatran initiator RD: 1.8%; warfarin initiator RD: 1.9%) appeared more harmful than nonexperimental results (dabigatran initiator RD: 0.14%; warfarin initiator RD: 0.57%). Conclusions: Differences in study populations can and should be considered quantitatively to ensure results are relevant to populations of interest, particularly when comparing trial with nonexperimental findings. See video abstract: http://links.lww.com/EDE/B703.
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Webster‐Clark et al. (2020) conducted an observational in atrial fibrillation. dabigatran vs. warfarin was evaluated on two-year risk differences for ischemic stroke, mortality, and gastrointestinal bleeding. Transporting trial results to a Medicare population yielded two-year mortality risk differences for dabigatran versus warfarin (-0.57%) closer to the null than nonexperimental methods (-1.9%).
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