Abstract
BackgroundHigh-sensitive real-time PCR assays are routinely used to monitor HIV-1 infected subjects. Inter-assay discrepancies have been described at the low viral load (VL) end, where clinical decisions regarding possible virological rebound are based.MethodsA retrospective study was performed to analyze frequencies of viral blips after transition to the COBAS Ampliprep/COBAS TaqMan v2.0 HIV-1 assay (Taqman v2.0) in patients with prior undetectable VLs as measured with the Roche Cobas Ampliprep Amplicor HIV-1 Monitor Test, v1.5 (Amplicor) and was evaluated in comparison to a group of patients monitored with the Abbott Real-time HIV-1 assay (Abbott RT) during the same period of time.Results85 of 373 patients with VLs below the limit of quantification with Amplicor had VLs >50 copies/mL after transition to the TaqMan v2.0 assay. Among these 74.1% had VLs ranging from 50–499 copies/mL, 22.9% had VLs >500 copies/mL. From 22 patients with initial Taqman v2.0 based VLs exceeding 500 copies/mL, 6 patients had VLs <20 copies/mL after novel VL measurement on a next visit. In our control group with VL quantification using the Abbott RT assay, only 1 patient became detectable and showed a VL of <40 copies/mL after new measurement.ConclusionsTransition to the Taqman v2.0 assay was accompanied by an increase of quantifiable HIV-1 VLs in patients with long term viral suppression under antiretroviral therapy that might be attributed to technical shortcomings of the Taqman v2.0 assay. A high test variability at the low VL end but also beyond was observed, making meaningful clinical interpretation of viral blips derived from different assays difficult.
Highlights
Viral load (VL) quantification constitutes a fundamental cornerstone of antiretroviral therapy management in HIV-1 infected subjects [1]
We have shown previously that the TaqMan v2.0 and the Abbott RT assay both allowed accurate determination of viral load levels in individuals infected with HIV-1 isolates that were found falsely negative or underestimated with the Roche CTM v1.0 assay [7]
Following the switch to the TaqMan v2.0 assay in the Vienna Center, multiple internal reports accumulated concerning an increase of detectable viral load (VL) in patients with previous long-term virological suppression
Summary
Viral load (VL) quantification constitutes a fundamental cornerstone of antiretroviral therapy management in HIV-1 infected subjects [1]. Ultrasensitive real-time (RT) -PCR assays for HIV-1 RNA quantification have been developed during the last years including the Abbott Real Time HIV-1 assay (Abbott RT, Abbott Diagnostics, Wiesbaden Germany) and the COBAS Ampliprep/COBAS TaqMan HIV-1 assay (TaqMan, Roche Diagnostics, Mannheim, Germany). Both test systems differ significantly regarding their extraction system, primer target region and probe design. We have shown previously that the TaqMan v2.0 and the Abbott RT assay both allowed accurate determination of viral load levels in individuals infected with HIV-1 isolates that were found falsely negative or underestimated with the Roche CTM v1.0 assay [7]. Inter-assay discrepancies have been described at the low viral load (VL) end, where clinical decisions regarding possible virological rebound are based
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