Comparison of the QUANTIPLEX HIV-1 RNA 2.0 Assay with the AMPLICOR HIV-1 MONITOR 1.0 Assay for Quantitation of Levels of Human Immunodeficiency Virus Type 1 RNA in Plasma of Patients Receiving Stavudine-Didanosine Combination Therapy

We compared the QUANTIPLEX HIV-1 RNA 2.0 assay with the AMPLICOR HIV-1 MONITOR 1.0 assay for quantitation of human immunodeficiency virus type 1 (HIV-1) RNA in plasma in the Stadi trail, which evaluated a stavudine plus didanosine combination therapy in 52 patients. HIV-1 RNA baseline values measured with AMPLICOR HIV-1 MONITOR 1.0 were significantly higher than those measured with QUANTIPLEX HIV-1 RNA 2.0, and decreases in HIV-1 RNA levels from baseline were also found to be significantly higher when measured with the AMPLICOR HIV-1 MONITOR 1.0 assay. The frequency of HIV-1 RNA levels below the lower limit of quantitation was significantly higher with QUANTIPLEX HIV-1 RNA 2.0 than with AMPLICOR HIV-1 MONITOR 1.0. Reanalysis of these results by an ultrasensitive procedure of AMPLICOR HIV-1 MONITOR 1.0 or by a modified version of the test that included additional primers adapted for non-B HIV-1 clades yielded greater differences between the QUANTIPLEX HIV-1 RNA 2.0 assay and the AMPLICOR HIV-1 MONITOR 1.0 assay. Our results indicate that a valid comparison of the virological efficacies obtained with different antiretroviral drug regimens requires the use of the same viral load quantitation procedure; further standardization between the different HIV-1 RNA quantitation kits is therefore needed.