Rates of and Reasons for Failure of Commercial Human Immunodeficiency Virus Type 1 Viral Load Assays in Brazil

We examined failures of commercial human immunodeficiency virus type 1 (HIV-1) viral load assays of 1,195 plasma samples from Brazilian patients. Assay failure was assumed for samples in which the virus was undetectable by commercial assay but which tested positive by real-time reverse transcription-PCR of the HIV-1 long terminal repeat (LTR) region or if the viral load differed by >2 log10 from that determined by LTR assay. Failure rates for Bayer Versant bDNA 3.0, Roche Amplicor Monitor v1.5, and bioMerieux NucliSens QT were 0.68, 0.47, and 4.33%, respectively. NucliSens may be inadequate for use in Brazil.