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Hepatitis C Virus Antibody and RNA Testing

Test code(s) 8472, 35645

Question 1. Where can I find the latest HCV management guidelines?

HCV management guidelines are provided by the American Association for the Study of Liver Diseases (AASLD) and the Infectious Disease Society of America (IDSA).1 These organizations publish joint, evidence-based recommendations on the Internet for rapid formulation and dissemination. For more information, visit http://www.hcvguidelines.org.

Question 2. For whom is HCV screening recommended?

The US Preventive Services Task Force (USPSTF) and the CDC recommend 1-time screening for HCV infection for adults born 1945 through 1965.2,3 One-time screening is also recommended for adults with high risk due to:

  • Injection drug use (current or former)3,4
  • Receipt of transfusions or organ transplants prior to July 19923,4
  • Having ever received long-term hemodialysis3,4
  • Incarceration3
  • Unregulated tattoo(s)3
  • Percutaneous (eg, occupational) exposure3,4
  • Receipt of clotting factor concentrates produced before 19873,4
  • HIV infection; the co-infection rate among this group is 20% to 30%5

Screening is also recommended for children born to HCV-positive mothers.3,4

Question 3. For whom is HCV testing (case finding) recommended?

HCV testing is recommended for individuals with persistently abnormal levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), or bilirubin.3,4

Question 4. What is the CDC-recommended HCV diagnostic algorithm?  

Please refer to https://www.cdc.gov/hepatitis/hcv/pdfs/hcv_flow.pdf.

Question 5. How do you interpret HCV antibody "reactive” and HCV RNA “not-detected” results?

A reactive HCV antibody test result combined with a not-detected HCV RNA result indicates no laboratory evidence of a current active HCV infection; no further action is required in most cases.

If distinction between a true positive and a biologic false-positive result for HCV antibody is desired, the CDC suggests that one can consider testing with another HCV antibody assay. If there is concern regarding the handling or storage of the test specimen, obtain a new sample for repeat testing.6

Question 6. Is it possible to have HCV infection and have a non-reactive HCV antibody test result?

Yes. Among persons with a non-reactive HCV antibody test, who are suspected of having liver disease or are at high risk of acute infection, testing for HCV RNA or follow-up testing for HCV antibody is recommended if high-risk exposure to HCV occurred within the past 6 months. Additionally, testing for HCV RNA can also be considered in persons who are immunocompromised (eg, persons who are receiving long-term hemodialysis or are HIV infected).

Question 7. What proportion of HCV antibody-reactive specimens are found to contain HCV RNA upon reflex testing of the same specimen?

Among specimens with reactive HCV antibody results, approximately 52% have detectable HCV RNA at a level of >15 IU/mL on reflex testing. However, the frequency varies markedly based on the strength of the signal of the antibody test, or signal-to-cutoff (S/C) ratio. Specimens with an S/C ratio of at least 1.0 are considered reactive for HCV antibody7 and thus undergo reflex testing for HCV RNA. Analysis of approximately 200,000 specimens submitted to Quest Diagnostics for HCV antibody testing with reflex to HCV RNA testing demonstrate that the frequency of positive reflex results increases with increasing S/C ratio:

Question 8. What do the following HCV RNA results mean: “<15 IU/mL Detected” or “<15 IU/mL Not Detected”?

The result “<15 IU/mL, Detected” means that HCV RNA is detected, although at a level (<15 IU/mL) that is too low to be quantified. This result could indicate current active HCV infection if consistent with other clinical and laboratory data. NOTE: If this test is being performed for HCV diagnosis, then this <15 IU/mL Detected result should be confirmed using a second sample from the patient.

In contrast, the result “<15 IU/mL, Not Detected” means that HCV RNA is not detected and there is no evidence of current active infection.

Quest Diagnostics measures HCV RNA viral load with the Roche cobas® HCV methodology. This is a quantitative real-time PCR assay with a lower limit of quantification (LOQ) of 15 IU/mL; the limit of detection (LOD) is slightly lower, at 10 IU/mL to 13 IU/mL. If the viral load is just at or above this LOD, but less than 15 IU/mL, the assay can determine that HCV RNA is present but cannot provide a reliable quantitative result. In such cases, the qualitative result of “<15 IU/mL, Detected” is provided.

Question 9. Why are HCV RNA results being reported in IU/mL? What does log IU/mL mean?

HCV RNA results are reported in IU/mL, which is the abbreviation for international units per milliliter. Results are reported in IU/mL to facilitate comparisons between results generated by different test methods. This is important because the various methods used by different laboratories are not standardized against each other. Use of IU/mL reporting units helps to make the comparison of viral load results across different methods more reliable.

HCV RNA results are also reported in log IU/mL, which is the logarithm of IU/mL. Results in this format make it easier to understand whether a change in viral load is clinically meaningful.

Replicating PCR test results using the same specimen can vary analytically by as much as 0.5 log IU/mL; thus, only changes greater than 0.5 log IU/mL from one measurement to the next (or across several measurements) are considered to represent true changes in viral load.8 Reporting the viral load results in log IU/mL units helps the healthcare provider accurately interpret changes in viral load and better assess a patient's response to antiviral treatment.

Question 10. I am treating my HCV-infected patient with direct-acting antiviral agents. The patient has detectable HCV RNA at a low level prior to completing treatment. How do I interpret these results and what would be the best next step for testing? 

If HCV RNA is detectable at week 4 of treatment, per AASLD guidelines, it is suggested to repeat quantitative HCV RNA viral load testing after 2 additional weeks of treatment. If quantitative HCV RNA testing at week 6 of treatment shows an increase of greater than 10-fold (>1 log10 IU/mL), discontinuation of HCV treatment is recommended. The cause of a positive HCV RNA test result at week 4, with decreasing levels at week 6 or week 8, is unknown. There is no recommendation to stop therapy or extend therapy for these patients.9

References

  1. AASLD-IDSA. HCV guidance: recommendations for testing, managing, and treating hepatitis C. http://www.hcvguidelines.org. Accessed September 2017.
  2. Centers for Disease Control and Prevention. Recommendations for the identification of chronic hepatitis C virus infection among persons born during 1945–1965. MMWR. 2012;61 (RR-4):1-32.
  3. US Preventive Services Task Force. Final Recommendation Statement: Hepatitis C: Screening. U.S. Preventive Services Task Force. December 2016.
    www.uspreventiveservicestaskforce.org/Page/Document/RecommendationStatementFinal/hepatitis-c-screening.
  4. Centers for Disease Control and Prevention. Recommendations for prevention and control of hepatitis C virus (HCV) infection and HCV-related chronic disease. MMWR Recomm Rep. 1998;47(RR-19):1-39.
  5. Panel on Opportunistic Infections in HIV-Infected Adults and Adolescents. Guidelines for the prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: recommendations from the Centers for Disease Control and Prevention, the National Institutes of Health, and the HIV Medicine Association of the Infectious Diseases Society of America. http://aidsinfo.nih.gov/contentfiles/lvguidelines/adult_oi.pdf. Accessed September 2017.
  6. Centers for Disease Control and Prevention (CDC). Testing for HCV Infection: an update of guidance for clinicians and laboratorians. MMWR Morb Mortal Wkly Rep. 2013;62:362-365.
  7. VITROS Immunodiagnostic Products Anti‑HCV Reagent Pack [package insert, version 13.0]. Rochester, NY: Ortho Clinical Diagnostics; 2017.
  8. Kleiber J, Walter T, Haberhausen G, et al. Performance characteristics of a quantitative, homogeneous TaqMan RT-PCR test for HCV RNA. J Mol Diagn. 2000;2:158-166.
This FAQ is provided for informational purposes only and is not intended as medical advice. A clinician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
Document FAQS.022
Version 3 effective 5/02/2018 to present
Version 2 effective 11/12/2014 to 5/02/2018
Version 1 effective 08/24/2013 to 11/11/2014
Version 0 effective 04/17/2012 to 08/23/2013