Background: The Abbott ViroSeq HIV-1 Genotyping System requires a minimum viral load of 2,000 copies/mL. The aim of this study was to evaluate the performance on samples of a viral load <2,000 copies/mL. Method: We performed a retrospective analysis of 780 genotypic tests performed at the University of Texas Medical Branch (UTMB) Molecular Diagnostics Laboratory between April 2007 and January 2008. Results: A quarter of the samples (25.5%, 199/780) had HIV viremia <2,000 copies/mL. Of the 199 specimens with plasma HIV RNA <2,000 copies/mL, genotyping was completed in 111 of 118 (94%) samples with quantifiable HIV RNA, but only in 48 of 81 (59%) specimens with a viral load <75 copies/mL. Conclusion: Our data does not support the conclusion of some investigators that HIV-1 genotypic resistance testing is technically unreliable on low viral load specimens.
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