Screening and Diagnosis
Transmission of HCV infection is associated with identifiable risk factors (Table 1), and most diagnoses result from screening of at-risk populations. All individuals with a risk factor for HCV infection should be tested. The appropriate screening test for HCV is serology (HCV antibodies), which indicates exposure to HCV, either current or past infection.
Current HCV infection should be confirmed by a polymerase chain reaction (PCR) assay for HCV RNA. About 25% of acute HCV infections will clear spontaneously within 6 months; these individuals continue to be HCV antibody-positive but do not have detectable HCV RNA in plasma. Criteria for PBS eligibility require evidence of chronic infection documented by repeated HCV antibody positivity and HCV RNA positivity. The clinical definition of chronic HCV infection is duration longer than 6 months. People with confirmed chronic HCV infection should be tested for HCV genotype. There are seven different HCV genotypes (Gt 1–7). The common genotypes in Australia are Gt 1 (50%–55%; 1a:1b = 2:1) and Gt 3 (35%–40%).21 As approved treatment regimens for HCV infection are genotype-specific, HCV genotyping is necessary before treatment initiation.
Annual HCV serological testing is recommended for seronegative individuals with ongoing risk factors for HCV transmission. For individuals who are seropositive but have undetectable HCV RNA (indicating past infection), annual HCV RNA testing is recommended only in the setting of ongoing risk factors for HCV transmission.