ICAAC: Viral load between six to 18 months predicts longer-term success of HIV therapy

A detectable viral load or treatment interruption six to 18 months after starting antiretroviral therapy is a predictor of poorer survival, impaired CD4 cell gain and ongoing HIV replication six years later, according to a Danish study presented to the 45^th Interscience Conference on Antimicrobial Agents and Chemotherapy in Washington DC last month.

Six months after starting anti-HIV therapy the majority of patients have overcome the initial side-effects associated with their treatment and achieved a viral load below 400 copies/ml. Danish investigators wished to see if virologic control of HIV during the next twelve months of antiretroviral therapy predicted mortality, CD4 cell gain, or subsequent HIV replication.

A total of 2046 patients were divided into one of three groups dependent on the amount of time they had a detectable viral load six to 18 months after starting anti-HIV treatment. Patients in group one never had a detectable viral load, those in group two had a detectable viral load 1% - 99% of the time and patients in group three always had a detectable viral load. The investigators then calculated six-year mortality rates and changes in CD4 cell count and viral load.

The patients provided almost 9,000 patient years of follow-up. Compared with patients who always had an undetectable viral load, individuals who had detectable HIV replication some of the time had an adjusted mortality rate of 2.6 per 100 patient years and patients with a detectable viral load all the time had an adjusted mortality rate of 4.6 per 100 patient years.

After six years, 93% of patients who always had an undetectable viral load six to 18 months after starting antiretroviral therapy were still alive, compared to 86% of patients who had an undetectable viral load some of time and 76% of individuals who never had an undetectable viral load between months six and 18 of treatment.

The investigators found that for patients with intermittent HIV control between months six and 18 of treatment, taking a break from antiretroviral therapy was associated with an increased risk of death (adjusted mortality ratio 3.48 per 100 person years).

CD4 cell count increased by a mean of 3 cells/mm³ for patients with 100% viral suppression between months six and 18, compared to 2.9 cells/mm³ for patients with intermittent viral control and 2.6 cells/mm³ for those individuals who never had viral suppression.

Nearly every patient (96%) who had 100% viral suppression between months six and 18 had a viral load below 400 copies/ml after six years of treatment, compared to 83% of those patients with occasional viral control and 57% of individuals with a constantly detectable viral load between months six and 18.