Evaluation of the performance of the automated NucliSENS easyMAG and EasyQ systems versus the Roche AmpliPrep-AMPLICOR combination for high-throughput monitoring of human immunodeficiency virus load

Abstract

This study presents the data of an evaluation of the automated Nuclisens easyMAG and EasyQ systems versus the Roche AmpliPrep-AMPLICOR combination for testing of high-volume human immunodeficiency virus (HIV) load. This represents a follow-up of a previous study investigating the performance of the real-time Nuclisens assay using the semiautomated NucliSENS miniMAG extraction procedure. Three hundred eighteen patient samples were analyzed using both methods. The easyMAG-EasyQ HIV type 1 system has a higher sensitivity and broader dynamic range than the Cobas AmpliPrep-AMPLICOR system when the standard Roche assay is used alone, 25 to 3,000,000 IU/ml versus 400 to 750,000 HIV RNA copies/ml, respectively. There was significant correlation between the assays (0.93; P < 0.0001), with good accuracy (percent similarity mean mu = 96%), good precision (percent similarity standard deviation = 4.97%), and overall good agreement with a low percent similarity coefficient of variation of 5.17 to 6.11%. Bland-Altman analysis revealed that the AMPLICOR assay generated higher values than the EasyQ combination, with 95% of results within clinically acceptable limits. The throughput of samples was greatly improved using the easyMAG-EasyQ system, allowing 144 samples to be processed within 6 h. The potential for contamination has been dramatically reduced using the automated extraction system. Additional negative controls have been added to the kit to monitor for contamination based on the South African experience. This assay thus presents a real option for monitoring HIV load assays in high-volume testing environments.

FIG. 1.

A scatter plot of the Roche AMPLICOR and EasyQ results reported in log IU/ml, showing the range in reported results and limits to each assay. The horizontal axis shows log IU/ml, and the vertical axis shows sample numbers in order of preparation for the total number of samples analyzed (n = 256).

FIG. 2.

Percent similarity histograms and Bland-Altman difference scatter plots for the total group (n = 256, left) and the trimmed group (n = 108, right). The histograms plot the frequency of the percent similarity values between the AMPLICOR and EasyQ results and show the number of similar results in each percent similarity interval. The normal curves are included, which visually show the accuracy between the methods (closeness of the peak to the 100% similarity line) and the precision (spread around the mean). The 100% similarity and 50 and 100% reference lines are also included. The summary statistics for these models are presented in Table 4.

FIG. 3.

Linear regression of one of the samples prepared in quadruplicate dilutions over log ranges to show linearity of the easyMAG EasyQ method. The horizontal axis shows the dilution number, and the vertical axis shows log intervals (IU/ml). The equation of the line is presented as well as the R², which shows that 96.7% of the data are represented by this equation. The %CV values for the quadruplicate results at each dilution are also given and show that the greatest variability occurs in the high and low ranges.