Infection: Hepatitis C virus; HCV; hep C
- Most new infectious in NZ are associated with intravenous drug use.
- Other risk factors include blood transfusion in NZ prior to 1992, migration or healthcare received from a high incidence country, incarceration, tattooing in non-licensed premises.
- Most infections are asymptomatic.
Did you know?
HCV is now highly curable due to potent new treatments. However, reinfection is possible, as immunity does not develop.
Who should I test?
Test for HCV in people with risk factors or abnormal liver tests.
Test of choice:
Depends on whether already known to have a positive antibody
Serology (HCV antibody) is the first line test for diagnosis in people who have not tested positive before. It indicates infection at some point in time.
- Excellent sensitivity – a negative test excludes hep C infection (unless exposure has occurred within the last few months).
- Excellent specificity – a positive result confirms infection with HCV at some stage, but does not necessarily mean the patient has active infection.
- In our laboratory, HCV core antigen is added on automatically to patient samples that test positive for HCV antibody, to determine active infection status.
- Excellent sensitivity – a negative antigen result excludes active infection in almost all people (HCV core antigen may be negative in people with lower viral loads, however this is uncommon). The combination of a positive HCV antibody with a negative core antigen/RNA indicates cleared/past infection.
- Excellent specificity – a positive result confirms active infection.
- HCV RNA also used to confirm cure from virus 12 weeks after completing treatment.
Tests to avoid/specialist tests:
HCV antibody testing in people who have tested positive in the past.
- HCV antibody remains positive life-long, even with clearance of the virus. Repeat testing does not give any information as to whether the person has active infection or not.
- Request HCV RNA or HCV core antigen if determination of active infection status is required in those who have had a positive antibody in the past.
- Because current treatments are effective on all genotypes this is no longer routinely required.