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IJE Advance Access originally published online on February 17, 2009
International Journal of Epidemiology 2009 38(3):746-756; doi:10.1093/ije/dyp004
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Published by Oxford University Press on behalf of the International Epidemiological Association © The Author 2009; all rights reserved.
The online version of this article has been published under an open access model. Users are entitled to use, reproduce, disseminate, or display the open access version of this article for non-commercial purposes provided that: the original authorship is properly and fully attributed; the Journal and Oxford University Press are attributed as the original place of publication with the correct citation details given; if an article is subsequently reproduced or disseminated not in its entirety but only in part or as a derivative work this must be clearly indicated. For commercial re-use, please contact journals.permissions@oxfordjournals.org

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

Benjamin H Chi1,2,*, Ronald A Cantrell1,2, Isaac Zulu3,4, Lloyd B Mulenga1, Jens W Levy1,2, Bushimbwa C Tambatamba5, Stewart Reid1,2, Albert Mwango6, Alwyn Mwinga3, Marc Bulterys3, Michael S Saag2 and Jeffrey SA Stringer1,2

1 Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.
2 Schools of Medicine and Public Health, University of Alabama, Birmingham, AL, USA.
3 US Centers for Disease Control and Prevention Global AIDS Program, Lusaka, Zambia.
4 School of Medicine, University of Zambia, Lusaka, Zambia.
5 Lusaka Urban District Health Management Team, Zambian Ministry of Health, Lusaka, Zambia.
6 Zambian Ministry of Health, Lusaka, Zambia.

* Corresponding author. Plot 1275 Lubutu Road, PO Box 34681, Lusaka, Zambia. E-mail: bchi{at}uab.edu


  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 (≥95%), suboptimal (80–94%) and poor (<80%).

Results Overall, 27 115 treatment-naïve adults initiated and continued ART for ≥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/µl vs 217 cells/µl; P < 0.001), 24 months (213 cells/µl vs 246 cells/µl; P < 0.001), 30 months (226 cells/µl vs 261 cells/µl; P < 0.001) and 36 months (245 cells/µl vs 275 cells/µl; 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.

Keywords HIV, adherence, medication possession ratio, mortality, survival, antiretroviral therapy, Africa, Zambia

Accepted 7 January 2009


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