A simple method to elute cell-free HIV from dried blood spots improves their usefulness for monitoring therapy

Abstract Background Dried blood spots (DBS) improve access to HIV viral load (VL) testing, but yield increased VL measurements compared to the plasma reference method because of cell-associated viral nucleic acid. In clinical settings, DBS methods may falsely categorize many patients as failing therapy. Objectives Description of a simple method, free virus elution (FVE), to preferentially elute plasma-associated virus from DBS samples with phosphate-buffered saline, and an initial HIV VL performance comparison with standard DBS elution methods. Study design The mechanism of action of FVE was studied with model DBS samples containing purified virus or washed HIV-containing cells, and with a DNA-specific HIV PCR. Using clinical samples, VL results from the new FVE method were compared to results from a dried fluid spot procedure (DFSP) protocol, which uses a guanidinium-based elution method, using plasma VL as the reference method. Results Model system experiments suggest that the method efficiently separates virus from cell-associated HIV, with a wide tolerance for incubation time and temperature. In 196 clinical samples, FVE reduced VL over-quantification from DBS, and improved DBS clinical concordance with plasma from 67% to 95%. Conclusions A simple elution in PBS significantly reduced the over-quantification of HIV VL in DBS. Additional studies are needed to validate the method in fingerstick-collected specimens and to further understand the compartmentalization of HIV DNA and RNA in DBS specimens.