False positive ultrasensitive HIV bDNA viral load results in diagnosis of perinatal HIV-infection in the era of low transmission

Background: The performance of ultrasensitive, quantitative assays in the diagnosis of perinatal HIV has not been documented in a population with low perinatal transmission due to use of antiretroviral therapy. Methods: We studied 205 plasma samples from 71 perinatally-exposed infants for HIV diagnosis using a quantitative branched DNA (bDNA) assay with a detection range of 75-500,000 copies/mL. Results: Twelve (16.9%) infants had at least 1 positive bDNA result. Two (2.8%) infants had confirmed HIV-infections as determined by ≥2 subsequent positive bDNA results (range=1,818-500,000 copies/mL). The remaining 10 (14.5%) infants had 1 positive bDNA test (range=81-440 copies/mL) with 2 subsequent negative bDNA tests and/or a negative HIV ELISA test; these infants were considered to have a false-positive result. The performance of internal assay standards was within acceptable limits. Conclusions: Our study suggests caution is needed in the interpretation of single, low-level, positive results of the ultrasensitive, quantitative bDNA test for HIV diagnosis of perinatallyexposed infants.