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Enhanced detection of low-level viremia by cobas 5800/6800 testing systems: a multi-center evaluation and clinical
Yu Wang1, Jianjian Li2, Pinliang Pan1
1National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
Introduction:
With the advent of more sensitive HIV-1 viral load (VL) testing systems, a greater number of low VL samples can be identified. However, for some patients who were previously virally suppressed, the new testing system may yield discordant results, posing challenges for clinical decision-making. This study systematically evaluated and compared the performance of the cobas 5800/6800 testing systems and the cobas AmpliPrep/cobas TaqMan (CAP/CTM) testing systems.
Methods:
The performance of the cobas 5800/6800 and CAP/CTM systems was assessed in terms of quantitative accuracy, precision, limits of detection, linearity, and clinical performance. A multi-center evaluation involving 18 sub-centers was conducted, and correlation and agreement analyses were performed on the quantitative results between the systems. The VL distribution among 1,486 patients in Yunnan Province was also analyzed to evaluate the impact of switching to the cobas 6800 system.
Results:
All the systems achieved a quantitative bias within 0.25 log and intra-run CV% below 5% at 10,000 and 1,000 IU/mL, while CAP/CTM demonstrated a CV% slightly exceeding 5% at 100 IU/mL. The limits of detection (cobas 5800/6800: 24 IU/mL; CAP/CTM: 30 IU/mL) matched manufacturer specifications, with all systems showing excellent linearity (R²=0.9965-0.9990) and subtype coverage. Correlation analysis showed strong associations (R²>0.90), yet the quantitative results of cobas 5800 and cobas 6800 showed a modestly higher, but consistent bias compared to CAP/CTM. Analysis of the VL distribution showed that switching to the cobas 6800 testing system significantly increased the proportion of VL between 20-200 copies/mL; however, no significant difference was observed after calculation using the correlation coefficient obtained from the multi-center evaluation.
Conclusion:
In summary, both the legacy and new testing systems exhibited excellent performance in detecting HIV-1 subtypes prevalent in China. This study provides reliable data to enable more accurate assessment of viral suppression efficacy during the transition period.