Residual HIV
viremia, defined by low levels of plasma HIV
RNA with enhanced-sensitivity assays, may persist even in the presence of successful antiretroviral
therapy, but little is known about its determinants. Our objective was to evaluate the rate and determinants of residual
viremia in patients who show stable undetectable plasma HIV-1
RNA with conventional assays. Forty-four multidrug-experienced patients with undetectable levels of HIV
RNA for at least 2 years under
raltegravir-based regimens were evaluated. An ultrasensitive (2.5 copies/ml) real-time PCR method was used to quantify plasma HIV
RNA. After 12 months of
salvage treatment, 48.3% of the patients had residual
viremia between 2.5 and 37 copies/ml. The proportion of patients with plasma HIV
RNA below 2.5 copies/ml decreased from 51.7% at 12 months to 30.8% at 24 months. The presence of residual
viremia was not associated with levels of
viremia before starting
raltegravir. Considering CD4 counts,
hepatitis B or C virus (HBV or HCV)
coinfection, or other demographic characteristics, for the time interval between HIV diagnosis and initiation of antiretroviral
therapy, patients with a longer interval (>1 year) were significant less likely to have
RNA levels below 2.5 copies/ml at 12 months compared to patients who started
therapy within 1 year of HIV diagnosis (28.6% vs. 73.3%, p=0.027). Half of the patients showing undetectable HIV
viremia with conventional assays had low-level
viremia with ultrasensitive assays, with no predictive role of viroimmunological status at the start of the regimen. The potential influence of the interval between HIV diagnosis and initiation of treatment should be confirmed in subjects with a known date of seroconversion.