Hepatitis C (HCV) antigen

Hepatitis C is a blood-borne, infectious viral disease that is caused by the hepatitis C virus (HCV). Clinically, it has two distinctive features:

  1. A high rate of symptomless acute infections, accounting for around three quarters of all cases.
  2. A high chronification rate of well over 50 % (estimates assume up to 90 % here) with possible liver cirrhosis and hepatocellular carcinoma later on.

Why Hepatitis C (HCV) antigen detection?
The HCV antigen is detectable before seroconversion, i.e. prior to the occurrence of HCV antibodies. This „diagnostic window”, meaning the phase when the virus is detectable but before any antibodies are present, can last up to 35 days and longer for HCV. A negative result for antibodies therefore does not rule out an early infection phase.

The presence of an active (acute or chronic) HCV infection is characterised by the presence of the HCV antigen (similar to the HBs antigen in an HBV infection).

After an acute infection has healed, HCV antibodies may still exist, but the HCV antigen brought about by the viraemia is no longer detectable.

Clinical application of the HCV antigen test

  • Screening of patients with a high risk of HCV infection, for example: dialysis patients, i.v. drug addicts
  • as an additional test for patients with evidence of anti-HCV in order to differentiate between an active infection and a healed infection
  • as a quantitative test to supplement monitoring of antiviral therapy

Comparison of anti-HCV and HCV antigens

Anti-HCVHCV antigen
Clinical useIndirect markers for diagnosing HCV infectionDirect markers for diagnosing HCV infection
Correlation to the PCR

None

Good

Detection delay compared to the PCR

35 days and more

0-10 days

Conclusions

  1. HCV antibody tests cannot distinguish between active and past infections, and they cannot be used for therapy monitoring.
  2. HCV antibodies are only detectable after a long delay. This is why the HCV antigen is a meaningful initial marker for recent infections, with a diagnostic sensitivity of 98.1 % and a specificity of 99.9 %.
  3. Determining the virus load by means of a quantitative PCR is still the most reliable marker for identifying an active/progressive chronic HCV infection in anti-HCV positive patients. Determining the presence of the HCV antigen may also be a meaningful supplement to detecting HCV replication in the blood in patients who are not undergoing therapy.

Test material
1 ml of serum


Literature

Gonzalez et al., 2005, J Viral Hepatitis 12: 481-487
Hayashi et al., 2005, J Viral Hepatitis 12 : 106-110
Mederacke et al. 2009, J Clin Virol 46 : 210-215
Seme et al. 2005, J Clin Virol 32 : 92-101

To top

Back