Recommended Testing Sequence for Identifying Current Hepatitis C Virus (HCV) Infection
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Interpretation of Results of Tests for Hepatitis C Virus (HCV) Infection and Further Actions
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Signal-to-Cut–Off Ratios for Commercially Available Assays
CDC has recommended that a person be considered to have serologic evidence of HCV infection only after an anti-HCV screening-test-positive result has been verified by a more specific serologic test (e.g., RIBA) or a nucleic acid test (NAT). This more specific, supplemental testing is necessary, particularly in populations with a lower prevalence of disease, to identify and exclude false positive screening test results. However, currently, the majority of laboratories report positive anti-HCV results based on a positive screening assay alone.
The recommended anti-HCV testing algorithm has been expanded to include an option that uses the signal-to-cut–off (s/co) ratios of screening-test--positive results. This can serve as an alternative to a supplemental test in some circumstances, minimizing the number of specimens that require supplemental testing and providing a result that has a high probability of reflecting the person's true antibody status.
Signal-to-cut–off ratios are calculated by dividing the optical density (OD) value of the sample being tested by the OD value of the assay cut-off for that run. Analysis of enzyme immunoassay and chemiluminescence assay data indicates that s/co ratios can be used to predict supplemental test-positive results. A specific s/co ratio can be identified for each test that would predict a true antibody-positive result (as defined by the results of supplemental testing) ≥95% of the time, regardless of the anti-HCV prevalence or characteristics of the population being tested.
Implementation of these recommendations will provide more reliable results for physicians and their patients, so that further counseling and clinical evaluation are limited to those confirmed to have been infected with HCV. This is especially critical for persons being tested for HCV infection for the first time, for persons being tested in non-clinical settings, and for those being tested to determine the need for medical referral. Implementation of these recommendations also will improve public health surveillance systems.
|Manufacturer||Assay Format||Signal-to-cut–off ratio predictive of a true positive ≥ 95% of the time|
|Ortho HCV Version 3.0 ELISA Test System||Ortho||EIA
|Abbott HCV EIA 2.0||Abbott||EIA
(Chemiluminescent Microparticle Immunoassay)
|Advia Centaur HCV||Bayer||CIA