Cross-contamination during processing of dried blood spots used for rapid diagnosis of HIV-1 infection of infants is rare and avoidable

Dried blood spot (DBS) samples are a convenient way to collect infant blood for HIV-1 diagnostic testing. Minimizing the risk of false positives is critical for diagnostic tests. A protocol for processing and testing DBS for infant HIV-1 diagnosis was evaluated to identify the rate and source of false-positive results. DES were created on Flinders Technology Associates (FTA) filter paper with 500 copies/punch (high) or 5000 copies/punch (very high) concentrations of HIV-1 DNA. Blank discs of filter paper punched after DBS samples were tested for carry-over of HIV-1 DNA using nested PCR for the pol region. No false positives were detected in the 40 series using high concentration DBS. In series with very high concentrations of HIV-1, 8/246 (3%) reactions were falsely positive. When tubes were spun prior to opening, contact with caps minimized, and spaces left between lanes of the gel, repeat second-round PCR of five false positives resulted in only one repeat false-positive PCR. This study outlines procedures that minimize false-positive results for nested PCR of HIV-1 DNA from DBS. (C) 2009 Elsevier B.V. All rights reserved.