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Prevalence of false-positive hepatitis C antibody results, National Health and Nutrition Examination Study (NHANES) 2007–2012

https://doi.org/10.1016/j.jcv.2017.01.007Get rights and content

Highlights

  • HCV RNA-confirmed chronic HCV infection prevalence overall (1%) was representative of the general US population.

  • Two percent of persons screened anti-HCV reactive; however, upon confirmatory testing:

  • Many anti-HCV tests were found to be false-positive (22%) or indeterminate (10%).

  • Half of anti-HCV reactive persons were HCV RNA negative, more than expected (20%) due to acute disease clearance alone.

  • All positive anti-HCV tests should be followed by an HCV RNA test for current infection.

Abstract

Background

Screening large numbers of persons in a population with low prevalence of a disease leads to many false-positives. However, populations with low HCV prevalence may sometimes be recommended for HCV screening, for instance patients or healthcare workers after a possible healthcare-related exposure.

Objectives

We determined the percentage of true vs false-positive HCV antibody (anti-HCV) test results among 2007–2012 participants in the National Health and Nutrition Examination Study (NHANES), a nationally representative study with approximately 1% HCV infection prevalence, much lower than in groups typically recommended for HCV screening.

Study design

Anti-HCV test confirmation was performed using a recombinant immunoblot assay (RIBA) test and follow-up HCV RNA testing.

Results

Overall, of 22,359 NHANES participants tested, 479 (2%) were anti-HCV screening reactive and 477 were tested for RIBA; of these 323 (68%) confirmed as true positive and 105 (22%) were false-positives. Many others (49, 10%) were RIBA indeterminate and likely false-positive. Because of these false positive tests, the overall prevalence of chronic infection among those testing anti-HCV screening reactive was much lower (218, 51%) than would be expected due to disease clearance alone (approximately 80%).

Conclusions

All screening anti-HCV positive tests should be followed by an HCV RNA test, in order to confirm whether the patient has current infection so that infected persons can be referred to care and treatment to avoid the significant morbidity and mortality associated with chronic HCV infection.

Section snippets

Background

Screening for HCV infection is recommended in the US for groups considered to be at risk for infection or with a higher prevalence of HCV infection than the general population [1]. Testing is recommended in certain situations for asymptomatic persons in the general population, such as baseline and follow-up testing of healthcare providers after a needlestick exposure or persons notified to receive bloodborne pathogen testing after a potential exposure resulting from an identified healthcare

Objectives

We sought to determine the prevalence of true vs false-positive anti-HCV screening tests among participants in the 2007–2012 National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of the US non-institutionalized civilian population [6].

Study design

NHANES survey methods have been described elsewhere [7]; during 2007–2012 an initial screening anti-HCV test was performed on all NHANES participants aged 6 years or older [6]. Testing for anti-HCV in serum or plasma was conducted using anti-HCV chemiluminescent assay (CIA) on VITROS automated immunodiagnostic platform (Ortho Clinical Diagnostics, Raritan, NJ). Signal-to-cut-off ratios (S/CO) ≥1.0 were considered to be anti-HCV reactive [8]. Reactive specimens were tested using a confirmatory

Results

Of 22,359 NHANES participants tested for anti-HCV by CIA during 2007–2012, 479 (2.1%) were anti-HCV reactive. Of these, 477 (99.6%) had a confirmatory RIBA test and were included in further analysis.

Discussion

Screening persons in a population with low prevalence of a disease leads to many false-positives that may have health, economic and psychological impacts on patients and providers. In this sample with 1% HCV infection prevalence, the predictive value positive of the test [5] was lower than in higher prevalence populations: about seven of every ten screening-reactive anti-HCV results (68%) were true-positives and two of ten (22%) false-positives. One in 10 (10%) was “indeterminate,” of which

Competing interests

None declared.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Ethical approval

Ethical approval for the National Health and Nutrition Examination Study (NHANES) was obtained from the National Center for Health Statistics (NCHS) Research Ethics Review Board (ERB). Written consent was obtained from participants.

Disclaimer

The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.

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