Prevalence of false-positive hepatitis C antibody tests in the National Health and Nutrition Examination Survey (NHANES), 2007-2012

Background: Screening large numbers of persons in a population with low prevalence of a disease leads to many false-positive test results. As hepatitis C virus (HCV) screening increases in the US, we can anticipate many false-positive results creating anxiety and confusion.

Methods: We determined the percentage of true vs false-positive HCV antibody (anti-HCV) test results among participants in a nationally representative study (NHANES) with low HCV infection prevalence using a confirmatory recombinant immunoblot assay (RIBA) test and follow-up HCV RNA testing.

Results: Overall, of 22,359 NHANES participants tested, 479 (2.1%) were anti-HCV screening reactive and were tested for RIBA; of 477 tested by RIBA, 323 (67.7%) were true positives (RIBA-positive), and 105 (22%) were false positives (RIBA-negative) (see Figure). Many others (49, 10.3%) were RIBA indeterminate of which only 2 (4.9%) represented active infection. Ultimately, of 424 with more (RIBA and HCV RNA) testing, 218 (51.4%) were confirmed as active HCV infections.

Conclusion: False-positive antibody assays may occur with great frequency when screening low HCV prevalence populations, emphasizing the need for �reflex� HCV RNA testing to avoid clinician and patient confusion and distress.