This test, based on detection of a 21-kDa protein made by a stable region of the HCV genome, may be used in research settings to aid in the diagnosis of HCV infection. It is a major component of the viral capsid. It is not clear whether it circulates freely or is only in viral particles. A commercial immunoassay to detect HCV antigen is available for research use only. Level strongly correlates with HCV RNA.
Normal range: Negative.
Use
To predict a sustained virologic response early during therapy (4 weeks), reaching an optimal performance at month 3. The determination of total HCV core antigen levels in serum constitutes an accurate and reliable alternative to HCV RNA for monitoring and predicting treatment outcome in patients receiving PEG " “interferon/ribavirin combination therapy.
Interpretation
Increased in hepatitis C exposure.
Limitations
Lacks sensitivity in early detection. HCV antigen has similar sensitivity in infection with all genotypes of HCV.