Early and late direct costs in a Southern African antiretroviral treatment programme: a retrospective cohort analysis

Abstract

Background: There is a paucity of data on the health care costs of antiretroviral therapy (ART) programmes in Africa. Our objectives were to describe the direct heath care costs and establish the cost drivers over time in an HIV managed care programme in Southern Africa.

Methods/findings: We analysed the direct costs of treating HIV-infected adults enrolled in the managed care programme from 3 years before starting non-nucleoside reverse transcriptase inhibitor-based ART up to 5 years afterwards. The CD4 cell count criterion for starting ART was <350 cells/microl. We explored associations between variables and mean total costs over time using a generalised linear model with a log-link function and a gamma distribution. Our cohort consisted of 10,735 patients (59.4% women) with 594,497 mo of follow up data (50.9% of months on ART). Median baseline CD4+ cell count and viral load were 125 cells/microl and 5.16 log(10) copies/ml respectively. There was a peak in costs in the period around ART initiation (from 4 mo before until 4 mo after starting ART) driven largely by hospitalisation, following which costs plateaued for 5 years. The variables associated with changes in mean total costs varied with time. Key early associations with higher costs were low baseline CD4+ cell count, high baseline HIV viral load, and shorter duration in HIV care prior to starting ART; whilst later associations with higher costs were lower ART adherence, switching to protease inhibitor-based ART, and starting ART at an older age.

Conclusions: Drivers of mean total costs changed considerably over time. Starting ART at higher CD4 counts or longer pre-ART care should reduce early costs. Monitoring ART adherence and interventions to improve it should reduce later costs. Cost models of ART should take into account these time-dependent cost drivers, and include costs before starting ART. Please see later in the article for the Editors' Summary.

Figure 1. Mean categorised total monthly costs from 36 mo before starting to 60 mo on ART.

Figure 2. The proportional change in mean total costs associated with ART adherence with 95% confidence intervals.

(A) The highest overall ART adherence quartile was compared with the lowest adherence quartile within each time interval (ART costs included and excluded) from 4 mo before starting ART to 60 mo on ART. (B) The highest lagged ART adherence group was compared with the lowest group (≥3 monthly versus ≤1 monthly refills in the previous 4-mo period) within each time interval from 4 mo before starting ART to 60 mo on ART.

Figure 3. The proportional change in mean total monthly costs over time associated with baseline CD4 cell count.

Baseline CD4 count was compared with the referent group (200 cells/µl) within each time interval from 4 mo before starting ART to 60 mo on ART with lighter blue indicating higher relative costs.

Figure 4. The proportional change in mean total monthly costs over time associated with overall ART adherence.

Overall ART adherence was compared with the referent group (75%) within each time interval from 4 mo before starting ART to 60 mo on ART with lighter blue indicating higher relative costs.