At Home Versus In Clinic INR Monitoring: A Cost Utility Analysis from The Home INR Study (THINRS)
ABSTRACTBackgroundEffective management of patients using warfarin is resource intensive, requiring frequent in clinic testing of the international normalized ratio (INR) Patient self testing (PST) using portable at home INR monitoring devices has emerged as a convenient alternative. As revealed by The Home INR Study (THINRS) event rates for PST were not significantly different from those for in clinic high quality anticoagulation management (HQACM) and a cumulative gain in quality of life was observed for patients undergoing PST.ObjectiveTo perform a cost utility analysis of weekly PST versus monthly HQACM and to examine the sensitivity of these results to testing frequency.Patients/InterventionsIn this study, 2922 patients taking warfarin for atrial fibrillation or mechanical heart valve, and who demonstrated PST competence, were randomized to either weekly PST (n 1465) or monthly in clinic testing (n 1457) In a sub study, 234 additional patients were randomized to PST once every 4 weeks (n 116) or PST twice weekly (n 118) The endpoints were quality of life (measured by the Health Utilities Index) health care utilization, and costs over 2 years of follow up.ResultsPST and HQACM participants were similar with regard to gender, age, and CHADS2 score. The total cost per patient over 2 years of follow up was $32,484 for HQACM and $33,460 for weekly PST, representing a difference of $976. The incremental cost per quality adjusted life year gained with PST once weekly was $5566 (95 CI, $11,490 to $25,142) The incremental cost effectiveness ratio (ICER) was sensitive to testing frequency: weekly PST dominated PST twice weekly and once every 4 weeks. Compared to HQACM, weekly PST was associated with statistically significant and clinically meaningful improvements in quality of life. The ICER for weekly PST versus HQACM was well within accepted standards for cost effectiveness, and was preferred over more or less frequent PST. These results were robust to sensitivity analyses of key assumptions.ConclusionWeekly PST is a cost effective alternative to monthly HQACM and a preferred testing frequency compared to twice weekly or monthly PST.
Journal of General Internal Medicine