Routine diagnosis of HCV infection is based on the detection of HCV IgG antibodies (evidence of infection in the past, but not current infection) and if HCV antibody positive, testing for the HCV RNA genome. HCV IgG antibody is positive in ongoing active infection and a recovered infection (via natural clearance or treatment). HCV IgG antibody is negative in the window of 45-68 days between HCV infection and seroconversion to HCV IgG. HCV RNA (by polymerase chain reaction, PCR) provides the diagnosis of an ongoing, active HCV infection. PCR assays are expensive, involve considerable technical skill and are labour-intensive. The Abbott ARCHITECT HCV antigen (Ag) assay detects a viral protein which surrounds the RNA genome. The test is less expensive and less time-consuming than PCR and identifies current HCV infection. In the same way that hepatitis B surface antigen (HBsAg) is used to test for current infection with hepatitis B, HCV antigen tests for current infection with hepatitis C. The Abbott ARCHITECT HCV antigen assay is not as sensitive as PCR for current infection. The sensitivity of the Architect HCV-Ag assay is reported to be 428 - 2,700 IU/mL HCV RNA, depending on the HCV genotype. In HCV antibody positive, HCV antigen negative samples, a PCR test will be performed if not previously tested.