Nearly half of patients in the general population who test positive for hepatitis C virus (HCV) do not have the disease, according to Dr. Anne Moorman and her associates.

From a sample of 22,359 National Health and Nutrition Examination Study participants, 479 people received positive HCV antibody test results from 2007 to 2012. Of this group, 477 participants underwent further follow-up testing using a recombinant immunoblot assay. RIBA testing confirmed positive test results for 323 participants, while 105 patients received negative test results and 49 received indeterminate test results.

Samples from participants who received positive and indeterminate RIBA results were then tested using newer HCV RNA testing, which has replaced RIBA as an HCV confirmation test. Of the 278 samples that were RIBA positive tested for HCV RNA, 216 were positive, and 62 were negative. Of the 41 RIBA-indeterminate samples tested, 2 were positive and 39 were negative. Total positive HCV occurrence was 218 out of 424 fully tested NHANES participants.

“False-positive antibody assays may occur with great frequency, emphasizing the need for “reflex” HCV RNA testing to ascertain current infection status,” the investigators noted.

Find the full study in the Journal of Clinical Virology ( doi: 10.1016/j.jcv.2017.01.007 ).