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Intermittent Viremia

Among patients treated with triple-drug therapy, viral-load "blips" occurred frequently but were not associated with virologic failure or development of resistance.

The phenomena of intermittent viremia, or viral-load "blips," are common in patients with otherwise well-controlled viral replication. Because their prognostic significance remains unclear, these events have been of major concern to both patients and caregivers. Drawing on evidence from 2 clinical trials, this study provides some much-needed information.

Researchers retrospectively analyzed data from 241 patients from ACTG 343 and 13 patients from the Merck 035 trial. Eligible patients in both studies were PI- and 3TC-naive at the time of enrollment in the original studies and achieved a viral-load nadir of less than 50 copies/ml in response to triple-drug therapy (AZT + 3TC + indinavir or d4T + 3TC + indinavir). Viral load was measured by an assay with a limit of detection of 50 copies/ml. A blip was defined as a detectable viral load followed by an undetectable one. Virologic failure was defined as 2 consecutive viral-load measurements of more than 200 copies/ml.

Of the 241 ACTG 343 patients included in this study, viral-load blips were observed in 96 (40%). Virologic failure occurred in 10 (10.4%) of the 96 patients who experienced blips and in 20 (13.8%) of the 145 patients who did not (relative risk, 0.76; 95% confidence interval, 0.29-1.72). In a subset of patients examined with an even more sensitive assay (limit of detection: 2.5 copies/ml), the median viral load in the 3 patients who experienced blips was 23 copies/ml versus less than 2.5 copies/ml in the 7 patients without blips (P=0.15). When this novel assay was used in the 13 patients from Merck 035, blips above 50 copies/ml were detected in 6 patients. Patients with blips had a slightly higher "steady state" of viral replication than did those without, but none of the patients had experienced virologic failure after a median follow-up of 4.5 years. Viral DNA sequences from 7 of the Merck 035 patients did not show evolution of drug resistance.

These results should be considered preliminary: the median follow-up after the first blip in ACTG 343 was only 46 weeks. However, the similar findings in the longer-term but smaller Merck 035 trial are encouraging. Of note, these cohorts comprised carefully selected PI-naive patients with relatively well-preserved virologic and immunologic control. Thus, the results cannot necessarily be generalized to patients with more advanced disease or to those receiving PI-sparing or salvage regimens.

How do these results affect clinical practice? Episodes of intermittent viremia should be used as an opportunity to reassess adherence. Patients who experience blips will require close monitoring but can be reassured that these phenomena do not necessarily signify treatment failure. Future prospective trials need to address exactly how much viral suppression is required to achieve durable virologic, immunologic, and clinical benefit.

— Helmut Albrecht, MD

Dr. Albrecht is Assistant Professor of Medicine, Division of Infectious Diseases, at Emory University School of Medicine in Atlanta.

Published in AIDS Clinical Care September 1, 2001

Citation(s):

Havlir DV et al. Prevalence and predictive value of intermittent viremia with combination HIV therapy. JAMA 2001 Jul 11; 286:171-9.

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