The association of adherence to antiretroviral therapy with healthcare utilization and costs for medical care

Abstract

Background: The association between antiretroviral adherence, healthcare utilization and medical costs has not been well studied.

Objective: To examine the relationship of adherence to antiretroviral medications to healthcare utilization and healthcare costs.

Methods: A retrospective cohort study was conducted using data from 325 previously antiretroviral medication-naive HIV-infected individuals initiating first antiretroviral therapy from 1997 through 2003. The setting was an inner-city safety net hospital and HIV clinic in the US. Adherence was assessed using pharmacy refill data. The average wholesale price was used for prescription costs. Healthcare utilization data and medical costs were obtained from the hospital billing database, and differences according to quartile of adherence were compared using analysis of variance (ANOVA). Multivariate logistic regression was used to assess predictors of higher annual medical costs. Sensitivity analyses were used to examine alternative antiretroviral pricing schemes. The perspective was that of the healthcare provider, and costs were in year 2005 values.

Results: In 325 patients followed for a mean (+/- SD) 3.2 (1.9) years, better adherence was associated with lower healthcare utilization but higher total medical costs. Annual non-antiretroviral medical costs were $US 7,612 in the highest adherence quartile versus $US 10,190 in the lowest adherence quartile. However, antiretroviral costs were significantly higher in the highest adherence quartile ($US 17,513 vs $US 8,690), and therefore the total annual medical costs were also significantly higher in the highest versus lowest adherence quartile ($US 25,125 vs $US 18,880). In multivariate analysis, for every 10% increase in adherence, the odds of having annual medical costs in the highest versus lowest quartile increased by 87% (odds ratio 1.87; 95% CI 1.45, 2.40). In sensitivity analyses, very low antiretroviral prices (as seen in resource-limited settings) inverted this relationship - excellent adherence was cost saving.

Conclusion: Better adherence to antiretroviral medication was associated with decreased healthcare utilization and associated costs; however, because of the high cost of antiretroviral therapy, total medical costs were increased. Combination antiretroviral therapy is known to be cost effective; lower antiretroviral costs may make it cost saving as well.

Fig. 1

Multivariate associations of baseline factors and adherence with total annualized medical costs in the first (highest) vs fourth (lowest) adherence quartile for 158 previously antiretroviral medication-naive patients initiating first antiretroviral therapy within Denver Health, 1997−2003. MSM = men who have sex with men; OR = odds ratio.

Fig. 2

Annual medical costs ($US, year 2005 values) overall and by category using three different antiretroviral medication pricing schemes in 325 previously antiretroviral medication-naive patients initiating first antiretroviral therapy within Denver Health, 1997−2003. AWP = average wholesale price; PHS 340B = US Public Health Service Section 340B Prescription Discount Program; Q = quartile of antiretroviral adherence (Q1 = highest adherence, Q4 = lowest adherence).