Real-world health care costs based on medication adherence and risk of stroke and bleeding in patients treated with novel anticoagulant therapy
BACKGROUND: With the lack of real-world evidence, the challenge for drugreimbursement policy decision makers is to understand medication adherencebehavior among users of novel oral anticoagulants (NOACs) and itseffect on overall cost savings. No study has examined and quantified theburden of cost in high-risk patients taking NOAC therapy.OBJECTIVE: To examine the association of cost with adherence, comorbidity,and risk of stroke and bleeding in patients taking NOACs (rivaroxabanand dabigatran).METHODS: A retrospective cohort study used deidentified data from a commercialmanaged care database affiliated with Optum Clinformatics DataMart (January 1, 2010-December 31, 2012). Patients aged 18 years andolder with ≥ 1 diagnosis of atrial fibrillation/flutter, > 1 NOAC prescription,6-month pre-index and 12-month post-index continuous enrollment, andCHA2DS2-VASc score ≥ 1 were included. Adherence was calculated usingproportion of days covered (PDC ≥ 80%) over an assessment period of 3,6, and 12 months and compared based on level of comorbidity, stroke,and bleeding risk. The adjusted annual health care costs per patient (drug,medical, and total) were calculated using multivariable gamma regressioncontrolling for demographic and clinical characteristics and comparedacross groups based on adherence over 12 months, baseline level ofcomorbidity, and risk of stroke and bleeding.RESULTS: Of 25,120 NOAC patients, 2,981 patients were included in thefinal cohort. Based on a PDC threshold of ≥ 80%, the adherence rate over3, 6, and 12 months was 72%, 65%, and 54%, respectively. For all timeperiods, the level of adherence significantly increased (P <0.001), with anincrease in stroke risk (based on CHA2DS2VASc scores of 1, 2-3, and 4+);comorbidity (Charlson Comorbidity Index scores of 0, 1-2, and 3+); and riskof bleeding (HAS-BLED scores of 0-1, 2, and 3+). Adjusted all-cause totalcost calculated for a 12-month period was significantly lower ($29,742 vs.$33,609) among adherent versus nonadherent users. Drug cost was higher($5,595 vs. $2,233) among adherent versus nonadherent patients but wasoffset by lower medical costs ($23,544 vs. $30,485) costs. The overall costsignificantly increased for patients with a high risk of bleeding and a highlevel of comorbidity.CONCLUSIONS: Adherence to NOAC therapy led to a reduction in overallhealth care cost, since higher drug costs were offset by lower medical(inpatient and outpatient) costs among adherent patients. Cost informationbased on adherence and risk of stroke and bleeding can help formularydecision makers to assess risk-benefit and help clinicians in developinginterventions to reduce patient burden.