U.S. and Ugandan scientists say counting the number of HIV viruses in the blood rather than relying solely on counting the number of circulating HIV-fighting CD4 immune system cells is a far better way to uncover early signs that antiretroviral drugs are losing their punch, and to signal the need to get patients on more potent treatments to keep the disease in check.

In a new study, the expert team compared treatment-failure predictability of the HIV so-called viral load test to the one that counts immune system CD4 cells to track the disease's progression in 1,133 HIV-positive, Ugandan men and women.

Viral load testing, the experts say, has long been considered the gold standard but has not been as widely used as CD4-testing in developing countries because at $20 to $50 per test, it costs at least four times more than the CD4 test.

But study results show that it is worth adopting more widely because it is more accurate in predicting treatment failure, according to lead study investigator and infectious diseases specialist Steven Reynolds, M.D., M.P.H.

Overall, viral load testing confirmed that 80 people (7.1 percent) were failing on drug treatments. A majority (62) of the treatment failures, however, were not detected by standard CD4 test counts. All participants were tested every six months for the three-year duration of the study.

However, CD4 testing by itself identified 125 treatment failures, most of which (107) were subsequently proven not to be failing by virologic monitoring. Only 18 infected people were correctly identified as patients with treatment failure by both tests. In general, drug treatment is considered a failure if it did not suppress viral particles in the blood to nearly undetectable levels.

Reynolds, a staff clinician at the U.S. National Institute for Allergy and Infectious Diseases, says the new results will hopefully lead to changes in HIV-monitoring and testing guidelines from the United Nation's World Health Organization.

"Our results clearly show that practicing current CD4 immunologic monitoring guidelines, as recommended by WHO, wrongly identifies drug failures in infected people and misses a large number of infected people who are failing and need to switch to more potent medications," says Reynolds, who is also a medical microbiologist.

Since 2004, Reynolds and his team of experts have been studying various means of preventing and treating the disease among 12,000 people in Rakai, Uganda.

Early study findings, he says, prompted the Rakai team to switch annual and bi-annual monitoring practices to viral load tests only, despite the increased costs.

"Detecting antiretroviral drug failures accurately and early is essential to avoiding HIV drug resistance, which could result in HIV disease progressing to AIDS and leading to illness and death," says Reynolds.

Reynolds explains that although patients can be switched to more potent drugs after a treatment failure, their HIV virus becomes resistant to the older regimen and they cannot go back.

"So switching limits their treatment options, and it also costs a lot more," he says. "And in developing countries with limited resources, maximizing the number of people and their duration on first-line therapy through adherence and monitoring is critical."

First-line drug regimens, he notes, usually consist of a cocktail of three drugs, usually zidovudine (AZT), lamivudine (3TC), and nevirapine (Viramune), which cost nearly $240 per year. The second-line, more powerful drug regimens, often made up of tenofovir (Viread), emtricitabine (Emtriva) and lopinavir (Kaletra, Alluvia) cost as much as $750 per year.

More than 90 percent of the 2 million people infected with HIV in Sub-Saharan Africa are currently taking first-line antiretroviral therapy.

In the study, conducted jointly by U.S. and Rakai Health Sciences Program researchers, the experts defined a drug failure as evident when a viral count per cubic millimeter of blood jumped to more than 10,000 copies, or when viral counts rose sharply, with back-to-back tests showing a rise of at least 400 copies per cubic millimeter of blood.

Blood testing for a strong immune response to the viral infection is measured by the number of CD4 cells and reported as a treatment failure if there is either a persistent CD4 count that is less than 100 per cubic millimeters of blood or if there is a steep drop of at least 50 percent in immune cells, or if CD4 levels fall below that of when drug therapy was started.

Evaluation of the WHO immunologic criteria for antiretroviral treatment failure among adults in Rakai, Uganda, by Steven Reynolds, Gertrude Nakigozi, Kevin Newell, Anthony Ndyanabo, Ronald Galiwongo, Iga Boaz, Thomas Quinn, Ronald Gray, Maria Wawer and David Serwadda.

 

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