Human immunodeficiency virus (HIV) and hepatitis B virus (HBV) are endemic in South Africa while hepatitis C virus (HCV) infection is rare. Two nucleic acid amplification technology platforms, the Procleix Ultrio Elite assay on the Panther instrument (Elite) and the cobas MPX assay on the cobas 6800 or 8800 system (MPX), are used worldwide. In 2015 these were evaluated in South African context.
Study design and methods: The sensitivity of HIV, HBV, and HCV was evaluated using reference panels and 2-fold dilutions of 51 positive plasma samples tested in 12 to 24 replicates. The 95% and 50% lower limits of detection (LOD) were estimated by probit analysis and window period (WP) risk days by the Weusten model. Specificity was established by testing 3646 blood donations individually and instrument performance by evaluating all runs.
Results: Specificity was 99.94% for MPX and 99.97% for Elite. The following 95% LODs (95% confidence intervals [CIs]) were estimated for MPX and Elite, respectively: HBV, 17.8 (10.9-33.9) and 47.9 (29.1-92.4) cp/mL; HCV, 21.9 (15.3-34.6) and 13.8 (8.9-24.0) cp/mL; and HIV, 8.3 (5.5-14.7) and 10.4 (6.9-18.2) cp/mL. On SA HBV and HIV dilution panels, relative sensitivity (range) of MPX was 3.20 (1.26-6.50) and 1.42 (0.26-2.72) fold higher than Elite. Downtime on cobas 6800 was 26 hours vs 6.6 hours on Panther (P < .001). We estimated infectious WPs for HBV, HCV, and HIV-1 at 13.8, 1.8, and 2.6 days for Elite and 10.3, 2.1, and 2.4 days for MPX.
Conclusion: Although MPX was significantly more sensitive for HBV, Elite was implemented due to instrument reliability during evaluation.
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