Evaluation of the use of dried spots and of different storage conditions of plasma for HIV-1 RNA quantification

Abstract

Objectives: The aim of the study was to evaluate the use of dried plasma spots to determine HIV-1 RNA viral loads. Methods: The viral loads of 30 liquid plasma samples were compared with those of corresponding dried plasma spots on filter paper (DPS-FP) and in tubes (DPS-T), both of which were left for 7 days at 22°C. Also, 10 liquid plasma samples with detectable viral load were stored at 4, 22 or 37°C for 7 days and five further liquid plasma samples were air-dried for up to 54h to assess the effects of temperature and the drying step on HIV-1 viral load. Results: The viral loads of the 30 liquid plasma samples correlated significantly with those of the paired dried spots DPS-FP and DPS-T, but with median losses of 0.64 and 0.69 log10 HIV-1 RNA copies/ mL, respectively, and a limit of detection of 3 log10 copies/ mL. The 10 liquid plasma samples stored for 1 week at 37°C showed a weaker correlation and had a significantly reduced median viral load (-0.92 log10; P=0.005) when compared with the viral load of the matched plasma stored at -80°C. Most of the loss happened during the drying step. Conclusions: Reliable measurement of HIV-1 RNA viral load requires good plasma storage conditions. HIV RNA stability was affected by desiccation and 1 week of storage at 37°C. However, our findings suggest that liquid plasma can be kept at 4 or 22°C for a week with no effect on viral load. © 2007 British HIV Association.