Fig 1.
Validation plan for the Xpert VL assay.
The three specimen types used for validating the Xpert VL assay and statistical methodology employed.
Fig 2.
Protocol for testing of the DPS and DBS on the Xpert VL assay.
Schematic of the use of dried viral spots (DVS) for quality management of the GeneXpert instrument with the Xpert HIV-1 VL assay.
Table 1.
Method comparison for the evaluation of Xpert VL compared to Taqman v2 and Abbott HIV-1 RT on the frozen SAVQA panel.
Fig 3.
Scatter plots showing comparison of log VL values for Taqman v2, Abbott HIV-1 RT and Xpert VL assay.
(A) Xpert HIV-1 (green) compared to Taqman v2 (blue) and Abbott HIV-1 RT (red) on plasma specimens. The vertical axis represents the log VL and the horizontal axis represents the sample number sorted by the Taqman v2 assay; B) Xpert HIV-1 plasma (blue) compared to Xpert HIV-1 whole blood (red) and Xpert HIV-1 DBS (green). The vertical axis respresents the log VL and the horizontal axis is sample number sorted by Xpert HIV-1 plasma VL values. The red dotted line in both plots highlights the 1000cp/ml clinical threshold.
Table 2.
Xpert VL assay precision and method comparison on clinical plasma specimens.
Fig 4.
Bland-Altman and Passing and Bablok regression scatter plots.
Xpert HIV-1 VL versus (A) Taqman v2 (n = 53) and (B) Abbott HIV-1 RT (n = 45); (1) Bland Altman difference plots show the mean bias (solid line) and confidence intervals (dashed line); (2) Passing and Bablok regression analysis show the regression line (solid) with confidence intervals (dashed). Legends highlight the bias and regression equation.
Table 3.
Clinical misclassification of the Xpert VL assay tested on plasma, whole blood and DBS specimens.
Fig 5.
A line plot showing the stability of dried viral spots (DVS) for instrument and assay verification.
The log VL reported on Xpert HIV-1 was measured on DVS stored at room temperature and -20C over 42 days.