Laboratory diagnosis

The classic algorithm for diagnosing infection with the hepatitis C virus (HCV) requires screening of serum or plasma for HCV antibody followed by detection of HCV RNA to confirm an active infection. Assays that detect and quantify HCV core antigen provide an alternative to testing for HCV RNA. Molecular assays to quantify the HCV RNA load, determine the HCV genotype, and detect drug resistance-associated mutations are established in well-resourced practice to inform and monitor antiviral therapy, although guidance on use and interpretation continues to evolve. Hepatitis C is now curable. To reduce the large number of undiagnosed individuals and facilitate transition into care and treatment, simplified diagnostic and monitoring algorithms need to be established. Novel strategies for sampling and transport (e.g. dried blood spots) and testing (e.g. single-step molecular platforms) have been developed that can complement and potentially circumvent the requirement for sophisticated laboratory infrastructure, and a diagnosis of active infection can now be achieved at point of care using a few drops of blood collected by finger-prick. The laboratory plays a key role in supporting validation, standardisation, and implementation of the new tools and methods required to facilitate expanded access to treatment and achieve the ambitious goal of global elimination.