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Multicenter Study
. 2009 Jun;38(3):746-56.
doi: 10.1093/ije/dyp004. Epub 2009 Feb 17.

Adherence to first-line antiretroviral therapy affects non-virologic outcomes among patients on treatment for more than 12 months in Lusaka, Zambia

Benjamin H Chi  1 , Ronald A Cantrell, Isaac Zulu, Lloyd B Mulenga, Jens W Levy, Bushimbwa C Tambatamba, Stewart Reid, Albert Mwango, Alwyn Mwinga, Marc Bulterys, Michael S Saag, Jeffrey S A Stringer
Affiliations
Multicenter Study

Adherence to first-line antiretroviral therapy affects non-virologic outcomes among patients on treatment for more than 12 months in Lusaka, Zambia

Benjamin H Chi et al. Int J Epidemiol. 2009 Jun.

Abstract

Background: High-level adherence to antiretroviral therapy (ART) is associated with favourable patient outcomes. In resource-constrained settings, however, there are few validated measures. We examined the correlation between clinical outcomes and the medication possession ratio (MPR), a pharmacy-based measure of adherence.

Methods: We analysed data from a large programmatic cohort across 18 primary care centres providing ART in Lusaka, Zambia. Patients were stratified into three categories based on MPR-calculated adherence over the first 12 months: optimal (> or =95%), suboptimal (80-94%) and poor (<80%).

Results: Overall, 27 115 treatment-naïve adults initiated and continued ART for > or =12 months: 17 060 (62.9%) demonstrated optimal adherence, 7682 (28.3%) had suboptimal adherence and 2373 (8.8%) had poor adherence. When compared with those with optimal adherence, post-12-month mortality risk was similar among patients with sub-optimal adherence [adjusted hazard ratio (AHR) = 1.0; 95% CI: 0.9-1.2] but higher in patients with poor adherence (AHR = 1.7; 95% CI: 1.4-2.2). Those <80% MPR also appeared to have an attenuated CD4 response at 18 months (185 cells/microl vs 217 cells/microl; P < 0.001), 24 months (213 cells/microl vs 246 cells/microl; P < 0.001), 30 months (226 cells/microl vs 261 cells/microl; P < 0.001) and 36 months (245 cells/microl vs 275 cells/microl; P < 0.01) when compared with those above this threshold.

Conclusions: MPR was predictive of clinical outcomes and immunologic response in this large public sector antiretroviral treatment program. This marker may have a role in guiding programmatic monitoring and clinical care in resource-constrained settings.

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Figures

Figure 1
Figure 1
Distribution of adherence to ART over the first 12 months on treatment among adults surviving to at least 12 months in Lusaka, Zambia, between April 1, 2004 and September 30, 2007. Adherence was measured by the number of days a patient had antiretroviral drugs available according to pharmacy refill data
Figure 2
Figure 2
Post-12-month mortality by adherence category for ART-naïve adults initiating ART in Lusaka, Zambia, between April 1, 2004 and September 30, 2007. Adherence was measured by the number of days a patient had antiretroviral drugs available according to pharmacy refill data. The numbers shown at the bottom of the graph represent the number of patients active in each adherence category at 6-monthly intervals. Perfect survival in the first 12 months is a result of our study design. To be eligible for inclusion in this analysis, patients had to remain alive, active, and on ART until at least 12 months
Figure 3
Figure 3
Immunologic and clinical responses by adherence category for ART-naïve adults initiating ART in Lusaka, Zambia, between April 1, 2004 and September 30, 2007, and remaining on ART for >12 months. These include (a) CD4+ lymphocyte count, (b) haemoglobin and (c) weight
See this image and copyright information in PMC

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