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Updated: Jun 2, 2026
A Protocol for Analyzing Hepatitis C Virus Replication
Published on: June 26, 2014
Improved reflexive testing algorithm for hepatitis C infection using signal-to-cutoff ratios of a hepatitis C virus
Keane K Y Lai1, Ming Jin, Shan Yuan
1Southern California Research Center for Alcoholic Liver and Pancreatic Diseases and Cirrhosis, Department of Pathology, University of Southern California, Los Angeles, CA, USA.
Background:
Chemiluminescence immunoassay (CIA) is used to detect hepatitis C virus (HCV) antibody status on the basis of signal-to-cutoff (S/Co) ratios. Positive results of antibody to HCV (anti-HCV) are followed by either recombinant immunoblot assay (RIBA) to confirm anti-HCV positivity or reverse transcription (RT)-PCR to detect viremia. We hypothesized that by analyzing S/Co ratios, we could determine a strategy to reduce unnecessary supplementary testing in our population.
Methods:
CIA was performed to screen for anti-HCV, and positive results were followed up with RT-PCR testing. Negative RT-PCR results were followed up with RIBA, whereas positive RT-PCR results were assumed to be RIBA positive. ROC curves were analyzed to determine the optimal S/Co ratios to predict HCV infection.
Results:
We determined the S/Co ratios on 34 243 veteran patient samples. We found that with the CIA method 9.0% of patients had positive test results for anti-HCV. An S/Co ratio <3.0 ruled out active HCV infection and exposure with 100% negative predictive value. When the S/Co ratio was ≥20.0, positive predictive values were 98.5% compared with RIBA results, and 81.0% compared with RT-PCR results.
Conclusions:
RIBA is not necessary to confirm negative or positive CIA anti-HCV if the S/Co ratio is <3.0 or ≥20.0, respectively. To confirm HCV exposure, samples with an S/Co ratio between 3.0 and 19.9 should be followed up with RIBA unless PCR testing has been performed and the result is positive. Samples with an S/Co ratio ≥20.0 or positive RIBA results should be further tested by RT-PCR to determine HCV viremia status.
