Confirmation of antibodies against hepatitis C virus by recombinant immunoblot: Is it really an improvement to abandon it?

Dear Editor,

In 2013, following discontinuation of the FDA-approved recombinant immunoblot assay (RIBA), the USA Centers for Disease Control (CDC) updated their HCV testing algorithm with the withdrawal of the RIBA as supplemental test for anti-HCV and the recommendation of using only nucleic acid amplification test (NAAT), following anti-HCV screening reactive result. Results of a meta-analysis published in 2017, showed that the specificity of the methods in use for screening of antibodies against hepatitis C virus (anti-HCV) was excellent,¹ accordingly, the 2017 World Health Organization (WHO) recommendations also suggested to perform NAAT for chronic HCV confirmation following a reactive HCV serological test,² excluding again RIBA from recommendations. Accordingly, recommendations recently published in this journal by a group of experts from several Spanish hospitals parallel WHO and CDC guidelines.³

There are several points to consider regarding these recommended guidelines:

Among most recent studies, the results of a study in Egypt in 2016,⁴ indicate the necessity of confirmation by RIBA in a country with a high prevalence of HCV infection because false positive screening results can occur quite frequently (28.6% in health care workers). On the other hand, a study carried out in a low HCV prevalence setting, published in 2017 by the Division of Viral Hepatitis National Center for HIV, Hepatitis, STD, and TB Prevention, at CDC,⁵ also indicates a high frequency of false-positive anti-HCV screening results (a false positive rate up to 22% was observed) stating that “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”.⁵ Then, despite high specificity performance of the tests, the occurrence of false positive screening results seems to be significant (up 20%) both in areas of high and low prevalence of HCV infection.

The decision to exclude confirmation by RIBA from diagnostic algorithms is partially based on the assumption that a test detecting viremia following a reactive result on an anti-HCV screening test will effectively discard false positive results. This assumption should be nuanced: Firstly, although NAAT testing will indirectly confirm a screening reactive result only in case it is positive, absence of viremia does not exclude the true presence of anti-HCV. Secondly, NAAT testing will not identify in any case patients who have contacted the virus in the past but successfully resolved the acute infection. With the withdrawal of supplemental test for anti-HCV, it became challenging to discriminate false-positive results from resolved HCV infection. The approach of performing NAAT on screening reactive samples, will indeed correctly identify acute or chronic infections, however, it will not correctly identify the true HCV status of all other persons. These persons will consequently receive very imprecise information about their real HCV status. It is not surprising, therefore, that three quarters of the Spanish hospitals surveyed by the authors of the revision cited above declare they still perform RIBA tests to confirm the reactive samples in the screening.³

Accurate interpretation of anti-HCV-reactive results and a clear distinction between past, resolved HCV infection and a false-positive results is needed because of several aspects. First, a false positive result may have significant consequences for the patient in terms of time and cost. Second, if previous contact with HCV is confirmed, the patient would require prevention advice and continuous monitoring since reinfection could occur. Third, in a quality health care system, it seems a legitimate demand from all patients to receive information of equal quality on the results obtained with laboratory diagnostic tests that have been prescribed and performed. Fourth, individuals with a false-positive anti-HCV result would be incorrectly banned from donating blood, having a psychological impact on these persons and an impact on the available blood supply. Finally, in the Public Health field, abandoning correct information on the true HCV status would be unacceptable, since this would generate prevalence data quite far from reality due to the false positive results, which are still frequent.

In conclusion, we cannot agree with the recommendation to exclude the confirmation of anti-HCV by RIBA tests from the diagnostic test algorithm for HCV infection. We strongly encourage test centers to continue confirmatory testing in order to preserve the excellent quality of care provided to their patients.