Hepatitis C laboratory tests
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The laboratory diagnosis of hepatitis C infection is first made by documenting positive [[serologies (anti-HCV antibodies), followed by HCV RNA quantification by PCR to determine the viral load and to differentiate chronic infection from remission.
Serologies and HCV RNA
The diagnosis of HCV is rarely made during the acute phase given that the majority of individuals infected are asymptomatic during this phase of the disease. Chronic hepatitis C may be suspected on the basis of the medical history (particularly if there is history of IV or intranasal drug use), a history of piercings or tattoos, unexplained symptoms, or abnormal levels of liver function tests found during routine blood testing.
Hepatitis C testing begins with serological blood tests used to detect antibodies against HCV in the majority of cases. Overall, anti-HCV antibody tests have a strong positive predictive value for exposure to the hepatitis C virus, but may miss patients who have not yet had seroconversion.[1] As anti-HCV antibodies indicate exposure to the virus, but cannot determine active infection, all patients with positive anti-HCV antibody tests must undergo HCV RNA quantification to determine the viral load. The HCV viral load is an important factor in determining active disease and the probability of response to therapy. It is not associated with disease severity or the likelihood of disease progression.
Rarely, HCV RNA quantification is performed without prior anti-HCV antibody testing. This is only indicated in patients with known past history of cleared HCV infection and previous seroconversion and in patients in an immunocompromised state.
Among individuals with confirmed HCV infection, genotype testing is recommended. HCV genotype testing is used tailor therapeutic regimen.[2]
Laboratory Tests
- HCV Enzyme-linked immunosorbent assay (ELISA)
- Positive within 4-10 weeks after infection
- False negatives can occur with HIV infection, chronic renal failure, and cryoglobulinemia
- HCV RNA
- Polymerase chain reaction (PCR) highly sensitive for confirming viremia
- Predicts response to therapy but not risk of progression
A single positive PCR test indicates infection with HCV. Negative tests usually do not require re-testing, except in cases with high clinical suspicion.
Follow-up testing for health care personnel exposed to HCV-positive blood
- For the source, perform baseline testing for anti-HCV.
- For the person exposed to an HCV-positive source, perform baseline and follow-up testing, including
- baseline testing for anti-HCV and ALT activity AND
- follow-up testing for anti-HCV (e.g., at 4–6 months) and ALT activity. If earlier diagnosis of HCV infection is desired, testing for HCV RNA may be performed at 4–6 weeks.
- Confirmation by supplemental anti-HCV testing of all anti-HCV results reported as positive by enzyme immunoassay.
References
- ↑ AASLD/IDSA/IAS–USA. Recommendations for testing, managing, and treating hepatitis C. http://www.hcvguidelines.org. Accessed July 27, 2014.
- ↑ World Health Organization (WHO) 2014. Guidelines for the screening, care and treatment of persons with hepatitis C infection.http://www.who.int/hiv/pub/hepatitis/hepatitis-c-guidelines/en/. Accessed online on July 24,2014.