Monitoring whether patients take medicines can help anticipate HIV treatment failure in Africa

May 20 2008

Information on how reliably people take their anti-HIV medicines can help identify those whose treatment will succeed or fail. Monitoring this information, which can be obtained directly from pharmacy records, works at least as well as performing blood tests that track the medicine's effect on the immune system, according to research published in PLoS Medicine by Gregory Bisson, Jean Nachega and colleagues at the University of Pennsylvania, Johns Hopkins Bloomberg School of Public Health, and the University of Cape Town.

Adherence, or taking medications exactly as prescribed, has long been known to be a key factor in the success of HIV treatment. In developed countries, success has been defined using blood tests to measure how well medications suppress the AIDS virus. These so-called viral load tests are often difficult to provide in developing countries, so alternatives are used, including CD4 T-cell counts, which indicate how well the immune system is responding to treatment. However, falling CD4 counts tend to indicate treatment failure only after the fact, often at a point when the virus has developed resistance and the patient's medications must be changed, typically to drugs that are more costly or difficult to take.

Working with an insurance plan that covers HIV treatment in 9 African countries, the researchers in this study calculated patient adherence from monthly claims for AIDS medicines actually dispensed by pharmacies, in proportion to the number of months that medicines were prescribed to the patient. Statistically comparing these adherence measures to CD4 test results in more than 1800 patients whose viral load results were available, they found that adherence was more accurate than CD4 counts in identifying individuals who went on to experience treatment failure over 6 months and 12 months of treatment.

These findings suggest that adherence assessments could be used for early identification of patients at high risk of treatment failure, averting its health impact and helping to prioritize limited viral load testing. Studies in other settings (such as public clinics where medication is provided without charge) are needed to confirm the general reliability of these findings.

These results do not change that fact that monitoring CD4 counts plays an important role in deciding when to begin HIV medications, or when to provide treatment to prevent conditions that occur at low CD4 counts. Nonetheless, according to the researchers, approaches to HIV treatment in resource-limited settings should include an adherence-based monitoring approach.

In an accompanying perspective article, David Bangsberg (University of California San Francisco, USA), who did not participate in the research, discusses the importance of proactive prevention rather than reactive response to HIV treatment failure.

Citation:Bisson GP, Gross R, Bellamy S, Chittams J, Hislop M, et al. (2008) Pharmacy refill adherence compared with CD4 count changes for monitoring HIV-infected adults on antiretroviral therapy.

PLoS Med 5(5): e109. doi:10.1371/journal.pmed.0050109