Background: Dried blood spots (DBS) are an easy way to collect and ship specimens for diagnostic testing of HIV. We developed a cost-effective, sensitive method for diagnosing acute HIV infection and infant infection using DBS and the Gen-Probe Aptima HIV-1 RNA Qualitative Assay.

Methods:  A PBS/detergent buffer was developed to elute the blood, including HIV-1 virions, from DBS. The limit of detection of the assay was tested using DBS made with spiked whole blood, DBS from HIV-1-infected and uninfected adults (n = 33 and n = 12, respectively), and DBS from infants (n = 138). Optimal pooling strategies were determined and then used to assess the ability of the pooled DBS assay to detect HIV infection in adults and infants.

Results: Using spiked whole blood, the limit of detection was ~400 copies/mL. However, when DBS from HIV-1-infected patients were tested, the assay proved to be more sensitive. All specimens from infected adults with detectable viral loads in the Roche HIV RNA assay (n = 25) (viral loads >50 copies/mL) and 28 of 29 specimens from infected infants were positive (viral loads >1000 copies/mL). In addition, 5 of 7 infected adults with viral loads <50 copies/mL were detected in the assay. The 1 false negative infant specimen was from a DBS that had been stored for 4 years at room temperature. All 120 specimens from uninfected adults and infants were negative (100% specificity). Pooling of as many as 50 DBS with a single positive punch was reactive in the assay if the positive punch had a viral load of at least 10,000 copies/mL. Greater sensitivity was achieved with a smaller pool size.

Conclusions:  The Gen-Probe Aptima HIV-1 RNA Qualitative Assay was successfully adapted to work with DBS. This assay could be used as a sensitive, specific, cost-effective way to determine acute infection in populations such as infants, vaccine recipients, blood donors, pregnant women, or sexually transmitted diseases clients.