Objective:

To examine the prevalence and clinical correlates of subsequently measurable viremia in HIV-infected patients who have achieved viral suppression below the limits of quantification (< 50 copies/ml).

Design:

Non-randomized dynamic cohort study of ambulatory HIV patients in nine HIV clinics in eight cities.

Patients:

Patients had two consecutive HIV-1 RNA levels< 50 copies/ml (minimum, 2 months apart) that were followed by at least two more viral level determinations while remaining on the same antiretroviral therapy (ART) between January 1997 and June 2000 (median 485 days). Transiently viremic patients were defined having a subsequently measurable viremia but again achieved suppression< 50 copies/ml.

Results:

Of the 448 patients, 122 (27.2%) had transient viremia, 19 (4.2%) had lasting low-level viremia and 33 (7.4%) had lasting high-level viremia (defined as 50–400 and> 400 copies/ml, respectively). Only 16 (13.1%) of those who had transient viremia later had persistent viremia> 50 copies/ml. The occurrence of transient viremia did not vary with whether the patient was ART-naive or experienced (P= 0.31), or currently taking protease inhibitors or not (P= 0.08). On consistent ART, the median percentage increase in CD4 cell count was statistically different between subgroups of our cohort (Kruskal–Wallis, P= 0.002).

Conclusions:

Transiently detectable viremia, usually 50–400 copies/ml, was frequent among patients who had two consecutive HIV-1 RNA levels below the limits of quantification. In this analysis, such viremia did not appear to affect the risk of developing lasting viremia. Caution is warranted before considering a regimen as ‘failing’and changing medications.