17 July 2012
Routine viral load monitoring among people taking antiretroviral therapy (ART) could lower both community viral load and HIV transmissions by one third, according to results of a mathematical modeling study involving people in southern Africa.
Because viral load testing is often costly and unavailable in resource-limited settings, clinicians must often monitor response to ART by tracking CD4 counts and clinical changes—an approach sanctioned by the World Health Organization. But much research shows that viral loads can be detectable for some time after CD4 or clinical changes signal a failing regimen. When a person continues taking the same regimen with a detectable viral load, resistance mutations can develop and that person runs a higher risk of transmitting HIV during sex.
Researchers developed a mathematical model to predict the course of individual viral load, CD4 response, and survival in 1000 HIV-positive people starting ART in southern Africa. Data for the model came from the International epidemiologic Databases to Evaluate AIDS (IeDEA) Southern African collaboration.
The investigators calculated cohort viral load as the sum of individual patient viral loads. They used the mathematical relationship between individual viral loads and transmission probability to estimate the number of new infections in these 1000 people.
If clinicians relied solely on CD4 count to monitor patients, cohort viral load would be 2,600,000 copies/mL and treated patients would transmit HIV an average of 6.3 times yearly.
Routine viral load monitoring would reduce cohort viral load 31% to 1,700,000 copies/mL. The number of yearly transmissions would also fall 31%, to 4.3. These 31% reductions in community viral load and annual transmissions held true when the researchers tested different scenarios in their mathematical model.
“Although routine viral load monitoring enhances the preventive effect of ART,” the authors note, “the provision of ART to everyone in need should remain the highest priority” in populations like the one studied here.
Source: Janne Estill, Cindy Aubrière, Matthias Egger, Leigh Johnson, Robin Wood, Daniela Garone, Thomas Gsponer, Gilles Wandeler, Andrew Boulle, Mary-Ann Davies, Timothy B. Hallett, Olivia Keiser, for IeDEA Southern Africa. Viral load monitoring of antiretroviral therapy, cohort viral load and HIV transmission in Southern Africa: a mathematical modelling analysis. AIDS. 2012; 26: 1403-1413.
For the study abstract
(Downloading the complete article requires a subscription to AIDS or an online payment; the abstract is free.)