title: Ability of two commercially available assays (Abbott RealTime HIV-1 and Roche Cobas AmpliPrep/Cobas TaqMan HIV-1 Version 2.0) to quantify low HIV-1 RNA Levels (<1,000 copies/milliliter): comparison with clinical samples and NIBSC working reagent for nucleic acid testing assays.
abstract: Concordance between molecular assays may be suboptimal at low HIV-1 viremia levels (<1,000 copies/ml); therefore, it may be difficult to define and compare virologic endpoints for successful and failed therapy. We compared two commercial assays (the Abbott RealTime HIV-1 and the Roche Cobas AmpliPrep/TaqMan HIV-1 version 2.0) for their ability to detect and quantify low viral loads. A comparison was performed using 167 residual clinical samples (with values ranging from "not detected" to 1,000 copies/ml, as measured by the Abbott assay) and the National Institute and Biological Standards and Control (NIBSC) HIV-1 RNA working reagent 1 for nucleic acid amplification techniques (NAT) assays (serially diluted to a range from 1 to 1,000 copies/ml). Quantitative results were compared using Lin's concordance correlation coefficient and a Bland-Altman plot. Concordance with the qualitative results was measured by Cohen's kappa statistic. With clinical samples, the degree of interassay concordance of the qualitative results at a 40-copies/ml HIV-1 RNA threshold was substantial (κ = 0.762); the correlation among the quantified samples was suboptimal (concordance correlation coefficient, 0.728; P < 0.0001); the mean difference of the values between the Roche and Abbott assays was 0.193 log10 copies/ml. Using the HIV-1 RNA working reagent 1 for NAT assays, the results provided by the Roche assay were, on average, 3 times higher than expected, while the Abbott assay showed high accuracy. The Roche assay was highly sensitive, being able to detect a level as low as 3.5 copies/ml HIV-1 RNA with 95% probability. The performance characteristics of each molecular assay should be taken into account when HIV-1 RNA threshold values for "virologic suppression," "virologic failure," "persistent low viral loads," etc., are defined and indicated in the support of clinical decisions.
authors.affiliation: National Institute for Infectious Diseases Lazzaro Spallanzani, Rome, Italy alessandra.amendola@inmi.it.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Amendola
authors.affiliation: National Institute for Infectious Diseases Lazzaro Spallanzani, Rome, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Marsella
authors.affiliation: National Institute for Infectious Diseases Lazzaro Spallanzani, Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Bloisi
authors.affiliation: National Institute for Infectious Diseases Lazzaro Spallanzani, Rome, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Forbici
authors.affiliation: National Institute for Infectious Diseases Lazzaro Spallanzani, Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Angeletti
authors.affiliation: National Institute for Infectious Diseases Lazzaro Spallanzani, Rome, Italy.
authors.forename: Maria R
authors.initials: MR
authors.lastname: Capobianchi
mesh_terms: D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000302:isolation & purification*; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D012367:RNA, Viral / Q000097:blood*; D012680:Sensitivity and Specificity; D019562:Viral Load / Q000379:methods*
chemical_list: D012367:RNA, Viral