Blood Tests Six Days After Initiating Antiretroviral Therapy Can Predict Treatment Efficacy
Measuring plasma HIV RNA levels six days after beginning antiretroviral treatment -- instead of the typical four to eight weeks -- can predict the success of the drugs in fighting HIV, possibly improving the efficacy of drug treatment and preventing drug resistance, according to a study in the Nov. 24 issue of the Lancet. Researchers from the National Institute of Allergy and Infectious Diseases and the National Cancer Institute analyzed the treatment histories of 124 HIV-positive patients who had taken part in three different studies between 1995 and 2000: 52 protease inhibitor-naive children who received monotherapy with indinavir, 38 protease inhibitor-naive children who received monotherapy with ritonavir and 34 adults, also naive to protease inhibitors, who received four-drug combination therapy including the protease inhibitor indinavir. Each patient's blood was drawn and analyzed daily over a three-month period. There were no significant differences in baseline HIV levels among the three groups. After comparing rates of decline in HIV levels over the first six days of treatment with treatment response after three months, the researchers found that 95% of the patients with rate of decline constants of less than 0.16 per day during the first six days after treatment initiation had a poor response to the therapy over time. Conversely, those with a rate of decline constant greater than 0.28 per day had a good response. "This finding suggests that the likelihood for poor or good response is very high (>95%) for changes in the HIV concentration of less than 0.96 log or higher than 1.68 log during the first six days on therapy," the researchers state, noting that a "much earlier assessment of drug efficacy might be feasible." Current treatment guidelines call for physicians to consider changing therapy if the reduction in plasma HIV RNA is less than 0.50-0.70 log after four weeks of treatment or less than 1.00 log by eight weeks of therapy. The researchers note that treatment adherence is a "major problem" in HIV therapy, and that their suggested approach can only be used effectively if "additional information on the adherence to the treatment is provided." They recommend prospective studies with larger homogenous cohorts and cohorts of patients who have previously received drug therapy to "define more accurately the limits" of their study (Polis et al., Lancet, 11/24). The researchers predicted that the six-day test could be part of testing practice in three to four years, once follow-up studies are conducted (Ross, AP/Orlando Sentinel, 11/23).This is part of the KHN Morning Briefing, a summary of health policy coverage from major news organizations. Sign up for an email subscription.