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Comparison of gen-probe aptima qualitative HIV-1 RNA to Roche AMPLICOR HIV DNA assays for HIV diagnosis using dried blood spots
S. Fiscus, T. McMillion, M. Schanz, J.T. Hawkins, J. Nelson
University of North Carolina-Chapel Hill, Microbiology & Immunology, Chapel Hill, United States
Background: HIV RNA and DNA assays have been adapted for use with dried blood spots (DBS). HIV DNA is the gold standard for infant diagnosis, but many international sites only have access to HIV RNA assays. HAART given to the mother or prophylactic antiretrovirals given to the infant may reduce the sensitivity of early infant diagnostics (EID) if RNA assays are used.
Methods: We tested 121 DBS from HAART-treated and drug-naïve adults [viral loads (VL) < 48 to >750,000 cp/ml] in both the Gen-Probe Aptima HIV RNA and Roche AMPLICOR HIV DNA assays. DNA assay: two 6 mm2 punches were added to 1 ml Roche wash buffer, rocked 1 hr, the supernatant removed, and Roche lysis buffer added. Following incubation at 60oC and 100oC each for 15 min, the DBS were removed and manufacturer's instructions followed. RNA assay: two 6 mm2 punches were eluted in 0.525 ml of a PBS/detergent buffer by rocking for 2 hr prior to testing in the Gen-Probe assay following manufacturer's instructions using 0.5 ml of eluate.
Results: There was 90% concordance between the two assays. 105 samples with VL < 48 to >750,000 cp/ml were concordant reactive. Four samples with VL < 400 cp/ml (n=3) and 441 cp/ml were concordant non-reactive. 26 samples had VL < 400 cp/ml: 15 were reactive in both assays, 3 were non-reactive in both, 6 were only reactive for DNA and 2 were only reactive for RNA. For samples with VL >400 cp/ml there were only 4 discordants: 2 were reactive only in the RNA assay (VL: 1586 and 313,448 cp/ml) while 2 were only reactive in the DNA assay (VL: 596 and 7367 cp/ml)
Conclusions: These data suggest that either assay can be used for EID although the HIV DNA seems to be somewhat more sensitive when VL is < 400 cp/ml.
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