669 Evaluation of a Commercially Available Ultrasensitive p24 Antigen Viral Load Assay in Samples from Patients Infected with Genetically Diverse HIV-1 from Different Geographic Settings R. Respess*1, A. Cachafeiro2, S. Fiscus2, D. Newman1, B. Branson1, O. Varnier3, M. Rayfield1, R. Downing4, D. Withum1, W. Stevens5, A. Tehe6, T. Dondero1 1CDC, Atlanta, GA; 2Univ of North Carolina, Chapel Hill; 3Univ of Genova, Italy; 4CDC-Uganda, Entebbe, Uganda; 5Univ of Witwatersrand and Natl Hlth Lab Service, Johannesburg, South Africa; and 6Projet RETRO-CI, Abidjan, Ivory Coast
Background: The expense and technical complexity of RNA viral load (VL) assays make them difficult to implement and routinely use for the clinical management of HIV infection in resource-limited settings. A simple, sensitive yet inexpensive HIV-1 quantitation kit based on previously described modifications of a p24 antigen assay has recently become commercially available (PerkinElmer Life Sciences, Boston, MA), and was evaluated in both B and non-B subtypes to determine whether it could be used as a substitute for VL assays in resource-limited settings.
Methods: Anonymized sera/plasma from persons infected with known HIV-1 B and non-B subtypes were blinded, tested in duplicate by Ultrasensitive p24 Antigen (UPTA), and compared with previously determined VL. Log 10 transformation of VL and the average duplicate UPTA test results were compared by Pearson product-moment correlation coefficient to assess strength of statistical relationship.
Results: UPTA and VL test results were strongly correlated overall for subtype B from the U.S. (n = 232, r = 0.56 [p < 0.0001], r2 = 0.31), subtype C from South Africa (n = 30, r = 0.66 [p < 0.0001], r2 = 0.34) and Malawi (n = 18, r = 0.76 [p = < 0.0002], r2 = 0.65), subtype A/G from Ivory Coast (n = 60, r = 0.40 [p < 0.0013], r2 = 0.16), and subtypes A (n = 34, r = 0.81 [p < 0.0001], r2 = 0.64) and D (n = 29, r = 0.73 [p = 0.0001], r2 = 0.51) from Uganda. Duplicate UPTA test results were also strongly correlated.
Conclusions: The UPTA and VL results were significantly correlated independent of subtypes tested indicating that UPTA could be a suitable substitute for HIV-1 RNA VL where genetically diverse strains exist. UPTA is potentially a user-friendly, less expensive approach to VL testing in resource-limited settings.
