title: 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.
abstract: 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.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  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.
authors.affiliation: Department of Infection and Immunity, Grahame Hayton Unit, Ambrose King Centre, London, United Kingdom. nigel.garrett@bartsandthelondon.nhs.uk
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Garrett
authors.forename: Vanessa
authors.initials: V
authors.lastname: Apea
authors.forename: Achyuta
authors.initials: A
authors.lastname: Nori
authors.forename: Ines
authors.initials: I
authors.lastname: Ushiro-Lumb
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Oliver
authors.forename: Guy
authors.initials: G
authors.lastname: Baily
authors.forename: Duncan A
authors.initials: DA
authors.lastname: Clark
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019380:Anti-HIV Agents / Q000494:pharmacology / Q000627:therapeutic use; D015331:Cohort Studies; D005260:Female; D005838:Genotype; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology; D015497:HIV-1 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012367:RNA, Viral / Q000097:blood*; D011933:Reagent Kits, Diagnostic; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D015203:Reproducibility of Results; D019562:Viral Load; D055815:Young Adult
chemical_list: D019380:Anti-HIV Agents; D012367:RNA, Viral; D011933:Reagent Kits, Diagnostic