New study following 12,574 individuals over the course of three years of HAART

Although clinical progression to AIDS of patients infected with Human immunodeficiency virus (HIV) has declined since the introduction of Highly Active Antiretroviral Therapy (HAART), there is little data on the changes in incidence of AIDS-defining events during the first few years of therapy.

A new study following 12,574 individuals over the course of three years of HAART and tracking the incidence and type of these AIDS-defining events appears in the February 28 issue of Archives of Internal Medicine.

Treatment with HAART results in a dramatic reduction in the incidence of AIDS and death in individuals infected with HIV, according to background information in the article. Many of the patients included in early studies on HAART had been exposed to prior treatment with one or more of the HAART medications (usually nucleoside reverse transcriptase inhibitors [NRTIs]) before beginning HAART. The current study is designed to determine if the pattern of clinical progression to AIDS and the pattern of decline in AIDS-defining clinical events, including which types of conditions appear to exhibit less rapid declines in incidence after initiation of HAART, are the same in individuals starting HAART therapy who have not been previously exposed to any of the medications used in HAART (anti-retroviral-naïve individuals).

Caroline A. Sabin, Ph.D., of the Royal Free and University College Medical School, London, and colleagues from the Antiretroviral Therapy Cohort Collaboration (ART), an international collaboration between the investigators of 13 cohort studies from Europe and North America, tracked 12,574 anti-retroviral-naïve individuals over the course of the first three years after starting HAART for events meeting the 1993 Center for Disease Control and Prevention criteria for AIDS. The AIDS-defining events were divided into five types, with different causes: viral, fungal, bacterial, protozoal or other. The incidence of new AIDS events was calculated as the number of events occurring in each of five periods (0 to 3 months, 4 to 6 months, 7 to 12 months, 13 to 24 months and 25 to 36 months after starting HAART) divided by the person-years of follow-up.

Patients in the study contributed a total of 22,928 person-years of follow-up during which time 928 AIDS events occurred. Seven hundred and ninety-two patients (6.3 percent) experienced at least one clinical event during the study period (680 patients experienced only a single event; 92, two different events; 16, three different events; and four, four different events). Three hundred twenty-five patients (2.6 percent) are known to have died; of these, 230 died without development of a new AIDS-defining event. The incidence of any AIDS event declined from 129.3 per 1000 person-years of follow-up in the first three months after starting HAART to 13.2 in the third year after starting HAART.

"In this large multicohort study we demonstrated a significant reduction of the incidence of opportunistic events, regardless of etiology (cause)," the authors conclude. "The pattern of decline was more pronounced for events of viral etiology and was maintained during the three-year follow-up. For events of viral, bacterial, and fungal etiology, this decline was greater than expected on the basis of changes in CD-4 count (a measure of immune function) and HIV-1 RNA level (a measure of level of virus in the blood), suggesting a benefit of HAART beyond the improvement of these surrogate markers."