Comparative performance of the amplicor HIV-1 monitor assay versus NucliSens EasyQ in HIV subtype C-infected patients

In facing global programs for treating HIV-infected patients in the developing countries, there is a real need for viral load assays that are accurate for the local subtypes. The present study was designed to evaluate viral load measurements using the newer version of the NASBA assay in subtype C-infected patients. The performances of this new version, a real-time nucleic acid sequence-based amplification HIV-1 assay (NucliSens EasyQ), were compared to Amplicor HIV-1 Monitor Assay version 1.5 in 79 samples of subtype C-infected patients originating from Ethiopia. Twenty HIV-1 subtype B-infected patients served as a control group. Blood samples from patients in both groups were tested by both assays. The results were compared by a paired, two-tailed Student's t-test. The disparity between the results of the two viral load assays was highly significant in subtype C samples (P=0.005), such that in the vast majority, higher values of viral load were obtained by the Amplicor assay. However, no differences between the two assays were found in subtype B samples (P=0.77). CD4 measurments were available for 78 samples of subtype C-infected patients. Of these, a CD4-to-viral load discrepancy (CD4 <= 200, viral load <= 5,000 IU/mI) was found in 11.5% of the samples when using the EasyQ assay, compared with 5.1% of the samples using the Amplicor assay. In conclusion, the performance of the NucliSens EasyQ assay was inferior to that of the Amplicor assay in assessing viral load levels in subtype C-infected patients. This difference may have a significant bearing on patient care.