title: At-Home Versus In-Clinic INR Monitoring: A Cost-Utility Analysis from The Home INR Study (THINRS).
abstract: Effective 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.
  
  
  
  To perform a cost-utility analysis of weekly PST versus monthly HQACM and to examine the sensitivity of these results to testing frequency.
  
  
  
  In 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.
  
  
  
  PST 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.
  
  
  
  Weekly PST is a cost-effective alternative to monthly HQACM and a preferred testing frequency compared to twice weekly or monthly PST.
authors.affiliation: Health Economics Resource Center, VA Palo Alto Health Care System, Palo Alto, CA, USA. CiaranPhibbs@va.gov.|Department of Pediatrics and Center for Primary Care and Outcomes Research, Stanford University School of Medicine, Stanford, CA, USA. CiaranPhibbs@va.gov.|Health Economist, VA Health Economics Resource Center, 795 Willow Road (152MPD), Menlo Park, CA, 94025, USA. CiaranPhibbs@va.gov.
authors.forename: Ciaran S
authors.initials: CS
authors.lastname: Phibbs
authors.affiliation: Health Services and Systems Research Program, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore.|Warren Alpert Medical School of Brown University, Providence, RI, USA.
authors.forename: Sean R
authors.initials: SR
authors.lastname: Love
authors.affiliation: Jerry L. Pettis VA Medical Center, Research and Development Service (151), Loma Linda, CA, USA.|Department of Internal Medicine, Loma Linda University, Loma Linda, CA, USA.
authors.forename: Alan K
authors.initials: AK
authors.lastname: Jacobson
authors.affiliation: VA Palo Alto Health Care System, Cooperative Studies Program Coordinating Center (151 K), Palo Alto, CA, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Edson
authors.affiliation: Health Economics Resource Center, VA Palo Alto Health Care System, Palo Alto, CA, USA.
authors.forename: Pon
authors.initials: P
authors.lastname: Su
authors.affiliation: VA Palo Alto Health Care System, Cooperative Studies Program Coordinating Center (151 K), Palo Alto, CA, USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Uyeda
authors.affiliation: Health Services and Systems Research Program, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore.|Durham VA Medical Center, Durham, NC, USA.|Division of General Medicine, Department of Medicine, and Center for Clinical Health Policy Research, Duke University Medical Center, Durham, NC, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Matchar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000554:Ambulatory Care Facilities / Q000191:economics* / Q000592:standards; D000925:Anticoagulants / Q000191:economics / Q000627:therapeutic use; D003362:Cost-Benefit Analysis / Q000379:methods* / Q000592:standards; D016903:Drug Monitoring / Q000191:economics* / Q000379:methods / Q000592:standards; D005260:Female; D005500:Follow-Up Studies; D006699:Home Care Services / Q000191:economics* / Q000592:standards; D006787:Hospitals, Veterans / Q000191:economics / Q000592:standards; D006801:Humans; D019934:International Normalized Ratio / Q000191:economics* / Q000379:methods / Q000592:standards; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012648:Self Care / Q000191:economics* / Q000379:methods / Q000592:standards; D014859:Warfarin / Q000191:economics / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: anticoagulants; atrial fibrillation; cost effectiveness; heart valve; randomized trials