title: Concordance of HIV-1 RNA Values by Amplicor and TaqMan 2.0 in Patients With Confirmed Suppression in Clinical Trials.
abstract: BACKGROUND
  The COBAS AMPLICOR HIV-1 MONITOR Test, version 1.5 (Amplicor) has been replaced with the COBAS AmpliPrep/COBAS TaqMan HIV-1 Test, version 2.0 (TaqMan 2.0), a real-time polymerase chain reaction human immunodeficiency virus type 1 (HIV-1) assay with higher sensitivity and broader dynamic range. HIV-1 RNA values at the 50 copies/mL cutoff drive major patient management decisions and clinical study outcomes.
  
  
  METHODS
  A total of 2217 samples were collected from 1922 HIV-1-infected subjects taking antiretroviral therapy for at least 48 weeks and had at least 2 consecutive samples with HIV-1 RNA <50 copies/mL by Amplicor from 7 recent clinical trials. HIV-1 RNA results were obtained from the Amplicor and TaqMan 2.0 assays in parallel by a reference laboratory.
  
  
  RESULTS
  The overall concordance between assay results was 96% at the cutoff of 50 copies/mL. However, statistically significant discordance at the 50 copies/mL cutoff was found between the assays for 3.9% of samples (n = 87). By TaqMan 2.0, virologic failure defined as HIV-1 RNA ≥ 50 copies/mL was reported for 2.8% more samples than Amplicor. Of these 87 samples, 68 samples fell within the predicted range of assay variability. Retesting of HIV-1 RNA by TaqMan 2.0 confirmed the discordance in only 28 of the 87 samples.
  
  
  CONCLUSIONS
  The TaqMan 2.0 assay reports fewer subjects below the clinical endpoint of HIV-1 RNA <50 copies/mL in HIV clinical trials than the Amplicor assay. This difference must be considered when assessing disease progression, designing clinical trials, and comparisons with historical trials that used the Amplicor assay.
authors.affiliation: Gilead Sciences, Inc, Foster City, California.
authors.forename: Will
authors.initials: W
authors.lastname: Garner
authors.affiliation: Gilead Sciences, Inc, Foster City, California.
authors.forename: Kirsten
authors.initials: K
authors.lastname: White
authors.affiliation: Gilead Sciences, Inc, Foster City, California.
authors.forename: Javier
authors.initials: J
authors.lastname: Szwarcberg
authors.affiliation: Gilead Sciences, Inc, Foster City, California.
authors.forename: Scott
authors.initials: S
authors.lastname: McCallister
authors.affiliation: Gilead Sciences, Inc, Foster City, California.
authors.forename: Lijie
authors.initials: L
authors.lastname: Zhong
authors.affiliation: Gilead Sciences, Inc, Foster City, California.
authors.forename: Mike
authors.initials: M
authors.lastname: Wulfsohn
mesh_terms: D000328:Adult; D005260:Female; D015658:HIV Infections / Q000175:diagnosis* / Q000821:virology*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008297:Male; D025202:Molecular Diagnostic Techniques / Q000379:methods / Q000592:standards*; D012367:RNA, Viral / Q000097:blood*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods / Q000592:standards*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019562:Viral Load / Q000592:standards*; D014766:Viremia / Q000175:diagnosis / Q000821:virology
chemical_list: D012367:RNA, Viral
keywords: Amplicor; TaqMan 2.0; discordant; viremia