Authors: Baser O, Andrews LM, Wang L, Xie L.
Objective: To compare adherence, healthcare costs and utilization of valsartan/amlodipine single-pill combination (SPC) and angiotensin-receptor blocker/calcium-channel blocker multiple-pill free-combination (ARB + CCB FC) therapy using real-world data.
Methods: A retrospective study (January 1, 2007 to April 30, 2009) was conducted using US commercial healthcare insurance claims. Patients were assigned to two cohorts: ‘valsartan/amlodipine SPC cohort’ and ‘ARB + CCB FC therapy cohort’. The primary endpoints were adherence and persistence. The secondary endpoints were 1-year healthcare costs and utilization.
Results: Out of 12,628 eligible patients 3259 (26%) were included in the valsartan/amlodipine SPC cohort and 9369 (%74) in the ARB + CCB FC cohort. Risk-adjusted adherence rates were higher for valsartan/amlodipine SPC patients [OR: 1.38, 95% CI: (1.24, 1.53)]. The Cox proportional hazard model showed that valsartan/amlodipine SPC cohort patients were less likely to discontinue medication (HR: 0.87, p<0.001). Comparison between the groups also yielded that total healthcare costs of valsartan/amlodipine SPC patients were 16-20% lower than ARB + CCB FC therapy patients (p<0.0001).
Limitations: Since claims data are collected for payment purposes rather than research purposes, the study is bound by limitations for the retrospective analysis. For example, the presence of a claim for a filled prescription does not indicate that the medication was consumed or taken as prescribed. Data on health behaviors and patient lifestyle were not available. Over-the-counter medications and clinical disease severity were not available in the dataset. Incorrect coding is also a possibility. However, we have used previously validated datasets where these effects are minimal. Heterogeneity of the sample may create bias in our estimates, however, we have used advanced statistical methods to control for observed and unobserved bias.
Conclusion: The real-world use of valsartan/amlodipine SPC was associated with better adherence and persistence relative to ARB + CCB FC therapy among patients with hypertension. Moreover, patients taking single-pill combination therapy had lower healthcare costs and utilization.
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