Comparison of the rate and size of HIV-1 viral load blips with Roche COBAS TaqMan HIV-1 versions 1.0 and 2.0 and implications for patient management.

Background: The Roche COBAS TaqMan HIV-1 version 1.0 (v1.0) real-time PCR test detects more low level viral loads (VL) compared to the previous Roche Amplicor version 1.5 assay. Due to under-quantification issues, the Roche TaqMan HIV-1 version 2.0 (v2.0) was introduced in 2009. Controversy remains on differences at the low VL end, where clinical decisions regarding possible viral escape are based.

Objectives: To compare the rate and size of VL blips with v1.0 and v2.0 in virologically suppressed patients and describe the impact of v2.0 on patient management.

Study Design: A cohort study of HIV-positive patients on antiretroviral therapy with a VL <50 copies/ml at the beginning and end of the study period (July 2008-February 2010). VL blips were compared during two consecutive 9-month periods, initially measured by v1.0, then v2.0. Genotypic resistance testing and treatment switches were described.

Results: 1037 of 2584 patients (73.1% male) with median age 43 years were included. 2465 VL samples were measured on v1.0 and 2206 on v2.0. 108 (10.4%) patients had blips on v1.0 (4.4% of samples) compared to 99 (9.5%) patients (4.5% of samples) on v2.0. Median log VL was 1.89 (78 copies/ml) for v1.0 and 2.06 (116 copies/ml) for v2.0 (p=0.002). Further characterisation of 11 samples detected no resistance and no treatment modifications were identified.

Conclusions: TaqMan v1.0 and v2.0 have similar blip rates, while blips are higher with v2.0. This study supports the strategy to increase the threshold of concern for VL blips on v2.0.