Discrepancies in diagnosis of incident HIV infection between antibody- and DNA-based tests in a phase III prevention trial in southern Africa

Dried blood spots (DBS) are widely used to test for HIV in a variety of research and service delivery settings; however, uniform guidelines regarding collection, storage and DNA extraction processes have neither been developed nor evaluated. Previously published reports suggested DBS may be stored at room temperature for up to 60 days, and intensive stability tests have shown that DBS can withstand high temperatures, humidity and freeze–thawing. During the implementation of a large randomized controlled trial (RCT) in southern Africa, with HIV acquisition as the primary endpoint, we observed 65 instances when DBS samples collected from the same day as a positive HIV antibody test yielded negative DNA polymerase chain reaction (PCR) results. The source of this discrepancy may have been due to inadequate specimen volume, filter paper or DNA extraction procedures, but were most likely due to storage conditions that have been reported as acceptable in other settings.