Effect of combination therapy on immunologic progression of human immunodeficiency virus at a population level.

There is accumulating evidence from clinical trials and cohort studies that highly active antiretroviral combination therapy is effective at halting immunologic and clinical progression of human immunodeficiency virus (HIV). Its impact at a population level is less well known because the regimes may be difficult to tolerate and compliance poorer. The authors make use of population data for almost all of the HIV-infected people in Scotland in 1997 who were under clinical care and monitor their response to therapy during the first year when these effective treatments became widely available. More than two thirds of the HIV-positive patients were on some form of antiretroviral therapy during the year. The authors show that all treated groups, even those who were on changing regimes, showed net improvement in immunologic status during the year. For the group of patients on triple or quadruple therapy, there was an average increase of more than 100 CD4 cells/mm(3) over the year, with other treatment groups showing more modest, but significant, increases.