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

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 degrees C. Also, 10 liquid plasma samples with detectable viral load were stored at 4, 22 or 37 degrees C for 7 days and five further liquid plasma samples were air-dried for up to 54 h 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 log(10) HIV-1 RNA copies/mL, respectively, and a limit of detection of 3 log,0 copies/mL. The 10 liquid plasma samples stored for I week at 37 degrees C showed a weaker correlation and had a significantly reduced median viral load (-0.92 log(10); P = 0.005) when compared with the viral load of the matched plasma stored at - 80 degrees C. Most of the loss happened during the drying step. Conclusions Reliable measurement of HIV- I RNA viral load requires good plasma storage conditions. HIV RNA stability was affected by desiccation and I week of storage at 37 degrees C. However, our findings suggest that liquid plasma can be kept at 4 or 22 degrees C for a week with no effect on viral load.