To analyze the correlation and consistency between two real-time fluorescent quantitative PCR assays in the detection of HIV-1 viral load and to obtain the performance criteria.

Three batches of each reagent with different lot numbers were selected to test serially diluted quantification control materials to assess the linearity and precision. Both reagents were also used to analyze 166 HIV-positive and 27 HIV-negative samples to compare the correlation and consistency between the two assays.

The coefficients of determination for serially diluted quantification control materials by COBAS AmpliPrep COBAS TaqMan HIV-1 test (version 2.0) and GeneXpert HIV-1 viral load assay were 0.978 (R²=0.978) and 0.987 (R²=0.987), respectively. The inter-batch and overall coefficients of variation of serially diluted quantification control materials were all <7%. There were no statistically significant differences in the results of serially diluted quantification control materials by different batches of both reagents. The test results of plasma samples indicated that the rate of agreement for negative samples was 100%. The observer agreement rate was 50% at the level of cut-off value, which was 40 cps/mL, indicating lacking of agreement reaching the lower limits by the two assays. Within the linear range, the coefficient of determination for the test results was 0.946 (R²=0.946). Bland-Altman analysis showed a mean difference of 0.41 log10 IU/mL.

Both assays showed good performance in the test and had well clinical equivalence for detection of HIV-1 viral load.

HIV-1; Viral load; Real-time fluorescent quantitative PCR