Adherence To HIV Medications Predicts Treatment Failure

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Main Category: HIV / AIDS
Also Included In: Immune System / Vaccines;  Infectious Diseases / Bacteria / Viruses;  Pharmacy / Pharmacist
Article Date: 19 May 2008 - 17:00 PDT

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According to a study published in the open-access journal PLoS Medicine, researchers are better able to predict whether a person's HIV treatment will succeed or fail if they have access to information indicating how reliably the patient takes the anti-HIV medicines. Gregory Bisson, Jean Nachega, and colleagues at the University of Pennsylvania, Johns Hopkins Bloomberg School of Public Health, and the University of Cape Town maintain that keeping track of this easily-obtainable information (from pharmacy records) is at least as effective as performing blood tests to track how the medicine affects the immune system.

In order for HIV treatment to be effective, patients must take medications exactly as prescribed - a practice called adherence. Successful adherence, in developed countries, is usually measured by using blood tests called viral load tests that assess how well the treatments are fighting the AIDS virus. As these tests are often not easily accessible in developing countries, doctors and program workers use alternative measures such as CD4 T-cell counts that shed light on the immune system's response to the treatment. The drawback of this test is that declining CD4 counts usually means that the treatment is failing and the virus has already developed resistance. At this point, the medications need to be changed - usually to drugs that are more expensive or difficult to take.

The multinational team of researchers set out to test how adherence measures from CD4 counts compared to adherence measures derived from monthly claims for AIDS medicines that were actually dispensed by pharmacies (relative to the number of months that the patients should have taken the medications). An insurance plan that covers HIV treatment in 9 African countries partnered with the researchers in administration and data collection, and results from CD4 counts and viral load tests were available in more than 1800 patients.

Statistical methods were used to compare the adherence measures, and the researchers found that the pharmacy refill adherence assessments were more accurate than CD4 counts in determining which individuals would experience treatment failure over 6 months and 12 months of treatment. These conclusions mean that adherence assessments may be an ideal tool for early identification of patients who are at a higher risk of treatment failure, resulting in the avoidance of adverse events and the ability of viral load testing to be prioritized and limited.

The researchers caution that although more tests are needed to generalize these results, the findings also do not diminish the importance of monitoring CD4 counts as a method of deciding when to begin HIV medications or when to treat low CD4 counts.

"The ability of adherence to identify patients at high risk of virologic failure early and to provide data on the behavior on which providers often wish to intervene should be considered a reason for clinics to organize these data in a way that can be used in simple algorithmic approaches to patient care," conclude the researchers.

An accompanying perspective article, written by David Bangsberg (University of California San Francisco, USA), writes:

"Antiretroviral treatment has transformed HIV from a terminal to a chronic disease in many regions of the world. Despite this important advance, relatively little progress has been made in monitoring missed doses, which are the proximal event to viral rebound and drug resistance. The report by Bisson and colleagues provokes a potential paradigm shift away from reactively responding to proactively preventing antiretroviral drug resistance."

Pharmacy refill adherence compared with CD4 count changes for monitoring HIV-infected adults on antiretroviral therapy
Bisson GP, Gross R, Bellamy S, Chittams J, Hislop M, et al.
PLoS Medicine (2008). 5(5): e109
doi:10.1371/journal.pmed.0050109
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A paradigm shift to prevent HIV drug resistance
Bangsberg DR
PLoS Medicine (2008). 5(5): e11
doi:10.1371/journal.pmed.005011
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About PLoS Medicine

PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit http://www.plosmedicine.org

About the Public Library of Science

The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org

Written by: Peter M Crosta
Copyright: Medical News Today
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