Cobas ampliprep/cobas TaqMan HIV-1 v2.0 assay: consequences at the cohort level

PLoS One. 2013 Aug 30;8(8):e74024. doi: 10.1371/journal.pone.0074024. eCollection 2013.


Background: High-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.

Methods: A 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.

Results: 85 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.

Conclusions: Transition 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.

MeSH terms

  • Antiretroviral Therapy, Highly Active
  • Cohort Studies
  • HIV Infections / drug therapy
  • HIV Infections / virology
  • HIV-1 / genetics*
  • HIV-1 / isolation & purification*
  • Humans
  • Reagent Kits, Diagnostic*
  • Real-Time Polymerase Chain Reaction / methods*
  • Taq Polymerase / metabolism*
  • Time Factors
  • Viral Load / genetics


  • Reagent Kits, Diagnostic
  • Taq Polymerase

Grants and funding

The authors have no support or funding to report.