New research has again confirmed the importance of viral load testing, which measures the amount of HI virus in the blood, to determine whether someone on antiretroviral (ARV) treatment is experiencing treatment failure and needs to be switched to a second-line drug regimen.
Regular viral load testing is standard practice in developed countries (an increased viral load indicates that a patient has developed resistance to one or more ARV drugs) but such tests are often unavailable in resource-limited settings because of their cost and a lack of laboratory capacity.
Health care providers instead rely only on CD4 counts (which indicate immune system strength) and clinical symptoms to decide whether a patient has stopped responding to first-line drugs.
HIV/AIDS experts have long been concerned that this method might miss large numbers of patients experiencing treatment failure, and could lead to the development of widespread drug resistance.
But new findings from the Academic Model Providing Access to Healthcare (AMPATH), an HIV/AIDS programme set up by the Indiana University School of Medicine in partnership with Moi University in Eldoret, western Kenya, suggest that the lack of viral load testing could also result in many patients being switched to more expensive second-line regimens unnecessarily.
Out of 149 patients suspected of experiencing treatment failure, based on a decline in their CD4 cell count of more than 25 percent, only 42 percent had detectable viral loads indicating that they needed to switch drugs. Even among 42 patients who experienced a CD4 count decline of more than 50 percent, only 24 had an elevated viral load, suggesting treatment failure.
Patients who had been on treatment for less than 12 months and still had a CD4 count of over 300 despite a decline were least likely to be experiencing treatment failure.
The AMPATH research, published in the 1 August edition of Clinical Infectious Diseases, reinforces results of a study in Uganda by the Johns Hopkins University Medical School and the Rakai Health Sciences Program.
The Ugandan findings, presented at a conference on Retroviruses and Opportunistic Infections in Montreal, Canada, in February 2009, also indicated that the use of CD4 counts to determine treatment failure often led to unnecessary changes in treatment regimens.
They suggested that dips in CD4 count could be the result of temporary infections such as malaria rather than the development of drug resistance, so putting patients on second-line ARVs, which cost between two and nine times as much as first-line drugs, could be wasting significant amounts of treatment programme budgets.
In the absence of viral load testing, the World Health Organization recommends switching a patient to second-line treatment if their CD4 count falls by more than 50 percent from its previous peak level, or if it persistently remains below 100. However, the researchers in Uganda suggested that the WHO criteria were inadequate for detecting true treatment failure.
In an editorial accompanying the AMPATH study findings, an HIV expert from Kenya and another from South Africa described "improved access to appropriate laboratory tests for initiating and monitoring ART [antiretroviral treatment]" in resource-limited settings as "a critical area of need".
But Fred Chiputula, coordinator of the Lighthouse clinic at Kamuzu Central Hospital in Malawi, a nongovernmental initiative which provides ARV treatment, commented that increasing the number of health facilities that can carry out viral load testing would be of little use unless healthcare workers received training on how to make use of such tests.
In Malawi, patients suspected of treatment failure are referred to central hospitals for viral load testing, specialized care and, if necessary, initiation on second-line treatment. "I’d say there is a need for more sites to have that facility [for viral load testing]," Chiputula told IRIN/PlusNews. "But just having the facility alone without experienced staff would be another challenge; you need to know how best that facility can be utilized."
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