Hepatitis C Virus RNA
Viral load monitoring for hepatitis C virus (HCV) is necessary to diagnose infection and monitor response to therapy. Detection of Hepatitis C virus RNA by polymerase chain reaction is recommended to confirm all positive HCV antibody tests. For more information see Hepatitis C Virus Antibody.
Currently available direct acting agents (DAA) for HCV can achieve a sustained virologic response (SVR), which is defined as the absence of detectable virus 12 weeks after completion of treatment. SVR is indicative of a cure of HCV infection. Virologic relapse is rare 12 weeks or longer after treatment completion. Over 90% of HCV infected persons can be cured of HCV infection regardless of HCV genotype, with 8 to12 weeks of oral therapy.
The introduction of DAA has decreased the need for assessment of HCV viral load during therapy. HCV RNA quantitation can minimally be done at baseline to establish the need for treatment and 12 weeks after initiation of therapy to assess SVR. More commonly HCV RNA testing is also done at 4 weeks to assess patient compliance.
Almost all patients with chronic HCV infection have HCV RNA concentrations greater than 1000 IU/mL. HCV RNA levels usually rapidly decline after initiation of treatment with DAA. Most patients who relapse will have HCV RNA concentrations above 1000 IU/mL at 12 to 24 weeks.
Most HCV RNA PCR assays target a well conserved 5' NTR region of the HCV genome and are calibrated to a WHO standard which has dramatically improved concordance between different assays. Sensitive HCV RNA PCR have a LLoQ of less than 10 IU/mL. HCV RNA can be detected in blood as early as 2 to 3 weeks after infection.
Many laboratories report results as both IU/mL and log 10 IU. All HCV testing guidelines refer to IUs. HCV copy number reporting is no longer appropriate.
Reference value is negative for HCV-RNA.
Specimen requirement is one SST tube of blood. Tubes containing heparin cannot be used. Serum needs to be separated from cells within six hours of collection and refrigerated or frozen to avoid degradation of viral RNA. Following separation, serum can be frozen and stored for prolonged periods.
References
https://www.hcvguidelines.org/evaluate/monitoring
https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/97291
https://www.hepatitisc.uw.edu/go/treatment-infection/monitoring/core-concept/all
