Evaluation of non-centrifuged dried plasma spots versus centrifuged and non-centrifuged plasma for determination of HIV-1 viral load

Accurate viral load measurement in plasma specimens is subject to the transport conditions applied since the stability of HIV-1 RNA can be at risk. Also, except during the primary infection, HIV is unlikely to be free in circulation because most patients produce specific antibodies in the weeks following primary infection. This study evaluated non centrifuged dried plasma spots versus centrifuged and non centrifuged plasma in the determination of HIV-1 viral load. A total of 40 patients infected with HIV were bled and three groups of samples were prepared from each patient. The first group was centrifuged at 1500 × g for 20 min, the second was not centrifuged but left to sediment by gravity for up to 3 h, and the third was for dried plasma spots prepared from the same non centrifuged plasma. HIV RNA quantitation in plasma and dried plasma spots was evaluated by the Pearson correlation and a T-test. The three groups yielded average viral loads of 58,249; 83,355 and 116,963 copies/ml for centrifuged, non centrifuged and dried plasma spot samples respectively. The correlation for centrifuged versus non centrifuged was R2 = 0.78, that of centrifuged and dried plasma spots was R2 = 0.72 and finally R2 = 0.81 between non centrifuged and dried plasma spot samples. A significant difference in viral load results of centrifuged and DPS samples prepared from non centrifuged plasma was observed.

► The correlation for centrifuged versus non centrifuged was R2 = 0.78, that of centrifuged and dried plasma spots was R2 = 0.72 and finally R2 = 0.81 between non centrifuged and dried plasma spot samples. ► A T test for centrifuged versus non centrifuged DPS samples indicated that the means of the two groups were significantly different. ► A T test for non centrifuged plasma versus non centrifuged DPS samples indicated that the means of the two groups were not significantly different. ► Non centrifuged plasma yields higher viral load which can allow usage of small volumes of samples such as those spotted on Whatman 903 filter cards. ► There is need for more research to determine whether non centrifuged plasma viral load values can be used as an indicator of treatment failure and disease progression in HIV-1 infected patients.