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An Analysis of Predictive Sample-to-Cutoff Index for HIV Infection Confirmation Using Elecsys® HIV Combi PT Assay
Xiaohong Xia1,2, Xiang Zhang3, Jun Zhou1,2
1Department of Laboratory Medicine, Branch of National Clinical Research Center for Laboratory Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
International Journal of Clinical Practice
|August 26, 2022
Summary
Adjusting the sample-to-cutoff index (COI) threshold for HIV testing significantly reduces false positives. This optimization enhances screening efficiency and lowers costs in low-prevalence settings.
Area of Science:
- Clinical diagnostics
- Infectious disease epidemiology
- Biostatistics
Background:
- Early HIV diagnosis is critical for effective prevention and treatment.
- Fourth-generation HIV detection assays exhibit a high false-positive rate (FPR) in regions with low HIV prevalence.
Purpose of the Study:
- To investigate the correlation between the sample-to-cutoff index (COI) and HIV confirmatory test results.
- To establish an optimized COI threshold for improved HIV infection prediction in a laboratory setting.
Main Methods:
- Retrospective analysis of primarily reactive HIV results using Elecsys® HIV combi PT assays.
- Confirmation of results via western blot (WB) and statistical comparison of COI values.
- Receiver operating characteristic (ROC) curve analysis to determine the optimal COI threshold.
Main Results:
- Out of 150,980 results, 305 were primarily reactive, including 82 true positives and 210 false positives.
- Mean COI for true positives (643.5) was significantly higher than for false positives (3.174).
- An optimal COI threshold of 9.87 was identified, yielding 100% sensitivity and 99.99% specificity.
Conclusions:
- Adjusting the COI threshold effectively reduces false-positive HIV screening results.
- Optimized thresholds increase screening assay efficiency, saving reagent, staff, and time costs.
- This approach improves the timely delivery of accurate HIV test results.
