https://immattersacp.org/weekly/archives/2013/05/14/5.htm

More follow-up testing needed for positive hepatitis C antibody tests

Clinicians should perform an RNA hepatitis C virus test to more definitively diagnose patients after a positive antibody test, the Centers for Disease Control and Prevention recommended.


Clinicians should perform an RNA hepatitis C virus (HCV) test to more definitively diagnose patients after a positive antibody test, the Centers for Disease Control and Prevention (CDC) recommended

The CDC updated its guidance this month because of the availability of commercial HCV antibody tests, evidence that many people with positive HCV antibody tests aren't being evaluated for current infection, and development of antiviral agents with improved efficacy.

Testing for HCV begins with a rapid or laboratory-conducted assay for HCV antibody in blood, the guidance states. A reactive result indicates current HCV infection, resolved past HCV infection or a false positive.

A reactive result should be followed by nucleic acid testing (NAT) for HCV RNA in one of four ways:

  • Blood from a subsequent venipuncture is submitted for HCV NAT if the blood sample collected is reactive for HCV antibody during initial testing.
  • From a single venipuncture, two specimens are collected in separate tubes: one tube for initial HCV antibody testing and a second tube for HCV NAT if the HCV antibody test is reactive.
  • The same sample of venipuncture blood used for initial HCV antibody testing, if reactive, is reflexed to HCV NAT without another blood draw for NAT.
  • A separate venipuncture blood sample is submitted for HCV NAT if the OraQuick HCV Rapid Antibody Test for initial testing of HCV antibody has used fingerstick blood.

If HCV RNA is not detected, that indicates either past, resolved HCV infection or false HCV antibody positivity. Testing to distinguish between true positivity and biologic false positivity may be done with a second HCV antibody assay that is different from the first assay used. Biologic false positivity is unlikely when multiple tests are used on a single specimen.

In addition to the new guidance, surveillance data on positive test results for HCV infection, reported to CDC from eight U.S. sites from 2005 to 2011, were analyzed in the MMWR.

Of 217,755 newly reported people, 107,209 (49.2%) were HCV antibody positive only, and 110,546 (50.8%) had a positive HCV RNA result that confirmed current HCV infection. In both groups, persons were most likely to have been born from 1945 to 1965 (58.5% of those who were HCV antibody positive only; 67.2% of those who were HCV RNA positive). The CDC amended testing recommendations in 2012 to include one-time HCV testing for everyone born from 1945 to 1965 regardless of other risk factors.