Molecular diagnostic tests for hepatitis C specifically detect HCV RNA and the process is commonly referred to as a Nucleic Acid Test (NAT) or Nucleic Acid Amplification Test (NAAT). In this circumstance, the RIBA could differentiate whether the patient had resolved HCV infection or had a biologic false-positive EIA. The RIBA antibody test, when it was available, was used as a follow-up test in persons who had a positive HCV EIA and a negative HCV RNA test. The RIBA test identifies specific antibodies generated in response to HCV antigens ( Figure 4) the test is interpreted as positive (2 or more antigens), indeterminate (1 antigen), or negative (0 antigens). Recombinant Immunoblot Assay (RIBA): The HCV RIBA is no longer recommended and is no longer available for use in the United States. ![]() Additional point-of-care rapid HCV antibody tests have been developed but are not approved for use in the United States. In 2011, the FDA granted a Clinical Laboratory Improvement Amendments (CLIA) waiver for the OraQuick HCV Rapid Antibody Test. The OraQuick test is read between 20 to 40 minutes after the test device is inserted into the buffer ( Figure 2) and the result is either reactive or nonreactive ( Figure 3). This OraQuick Rapid Antibody Test can be used as an alternative to the third-generation EIA for initial HCV antibody testing. Food and Drug Administration (FDA) in 2010 as a point-of-care test for use with whole blood samples obtained either by venipuncture or fingerstick. Point-of-Care Rapid Immunoassays: The OraQuick HCV Rapid Antibody Test was approved by the U.S.For the diagnosis of HCV, the CIA has similar sensitivity and specificity as the third-generation EIA. Chemiluminescence Immunoassay (CIA): The CIA test is an antibody test similar to the EIA, but is used less frequently than the EIA test.In addition, a false-positive test is more likely when performing widespread testing in populations that have a very low HCV prevalence. Specificity of EIA and False-Positive Results: The third-generation HCV EIA has a reported specificity greater than 99% false-positive tests can occur with increased gamma globulin production, with autoimmune diseases, and following immunizations.Circumstances associated with a false-negative EIA include patients with acute HCV infection, persons with major immunosuppression (advanced HIV infection or organ transplantation recipients), and persons with chronic renal failure on long-term hemodialysis. Sensitivity of EIA and False-Negative Results: The third-generation HCV EIA has a sensitivity of approximately 98%. ![]() The EIA test is reported as positive or negative based on an absorbance signal compared with a cut-off value.
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