O115. Low-level residual viremia and risk of virological failure

Purpose

The clinical relevance of residual low level viremia (LLV) in patients on steady HAART is debated. Similarly the clinical usefulness of HIV-RNA cut-offs lower than 50 copies/ml is questioned. Aim of this study was to analyze the dynamics of LLV in patients on HAART by means of a high resolution test for HIV-RNA.

Methods

This is a prospective, single-center, cohort study in patients on stable HAART (mean time on HAART 109 months, SD 28). All patients with a confirmed viremia <50 copies/ml were enrolled. Patients were monitored prospectively with determinations of HIV-RNA every 4 months performed with an enhanced PCR test with a lower limit of detection of 3 copies/ml. ITT analysis is reported.

Results

A total of 505 patients (78% males) with a mean age of 45.6 years (SD 7.6) were enrolled. At baseline the mean CD4 count was 667 cells/µl (SD 268) and VL was < 3 copies/ml in 73.9% and between 3 and 50 copies/ml in the remaining 26.1% of cases. Over the following 8 months period, patients with a baseline VL < 3 copies/ml presented a stable HIV-RNA below this threshold in 72.8% of cases, a level between 3 and 50 copies/ml in 27.2% of cases while no patient steadily rebounded above the 50 copies/ml threshold. On the contrary, patients with a baseline HIV-RNA between 3 and 50 copies/ml, in the follow-up, presented a stable VL < 3 copies/ml in 43.8% of cases, a VL between 3 and 50 copies/ml in 53.1% of cases, while 3.1% of patients steadily rebounded above the 50 copies/ml threshold (P < 0.0001). In the multivariate analysis the only variable significantly associated with viral dynamics was the third drug in the HAART regimen. A steady VL < 3 copies/ml, a VL between 3 and 50 copies/ml or a steady VL > 50 copies/ml was detected, respectively, in 71.8%; 27.7% and 0.6% of NNRTI-treated patients, while the same figures for PI-treated subjects were 56.2%; 42.9% and 1.0% (P = 0.029).

Conclusions

The presence of a LLV is associated to a low risk of virological failure; however, in selected patients it may be indicative of effective virus replication leading to virological rebound. Patients treated with a NNRTI-based HAART compared to those receiving a PI-based regimen show a statistically significant more pronounced and steady control of viral replication. Further, prolonged studies are needed to assess the clinical relevance of residual LLV and eventually define new cut-off values predictive of a better control of virus replication.