HIV-1 viral load: comparative evaluation of three commercially available assays in Argentina

RESUMO

Viral load (HIV-RNA copies per milliliter of plasma) has good correlation to prognosis considering progression to AIDS. The evaluation of commercial kits to measure viral load has become a need to find the most specific, sensitive and reproducible procedure to follow up HIV-infected patients. Hereby, a comparative analysis was done by using three different assays available in Argentina for quantitation of HIV-RNA in plasma. A plasma panel: 20 from HIV-1 infected individuals (9 asymptomatic and 11 symptomatic) and 9 from HIV-1 seronegative individuals was studied. Samples were run by Amplicor HIV-1 Monitor (Roche Diagnostic System, USA) Quantiplex HIV-1 RNA 2.0 Assay (Chiron Corporation, USA) and NASBA HIV-1 RNA QT (Organon Teknika, Holland). RNA was extracted from 0.2 ml of plasma for Amplicor, 0.1 ml and 1 ml of plasma for NASBA and, duplicates of 1 ml of plasma was centrifuged and pellet was used for bDNA assay no RNA extraction step. For a given specimen, a log difference of <0.5 between assays was considered as concordant result. All seronegative samples were bellow the detection limit of all assays (Amplicor 200 c/ml, NASBA 400 c/ml and Quantiplex (bDNA) 500 c/ml). Two samples from asymptomatic patients were not detectable by NASBA (Sensitivity: 90 per cent) Sensitivity was increased to 100 per cent by using 1 ml of plasma. All samples were detectable by the other assays (sensitivity: 100 per cent). For NASBA-bDNA, 74 per cent samples were concordant, 35 per cent for Amplicor-bDNA and 53 per cent for NASBA-Amplicor. By using 1 ml of plasma from asymptomatic patients, concordance was 65 per cent for NASBA-bDNA and 60 per cent for NASBA Amplicor. Comparing samples from asymptomatic patients, only 22 per cent was concordant in both cases. Reproducibility of NASBA was low (33 per cent, with differences lower than 0.5 Log) when 0.1 and 1 ml were used. Due to the levels of concordance of these results, it would be suggested to use always the same technique to follow up HIV-1 infection. The reproducibility of the assays should be tested by every laboratory and for every technician in charge of the assay in order to have confidence in the results specially to follow up HIV-infected patients or to monitor anti-viral therapies.