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Of all individuals infected with hepatitis C virus (HCV), about 75% of them will develop chronic hepatitis C with ongoing viral replication in the liver and detectable HCV RNA in serum or plasma, eventually resulting in cirrhosis. The remaining 25% of the infected individuals recover from the infection without evidence of viral replication or presence of detectable HCV RNA in serum or plasma.
In patients with chronic HCV infection, the response to combined interferon-alpha and ribavirin therapy is correlated with pretreatment serum or plasma HCV RNA levels (viral load) and HCV genotype. The optimal duration of combined interferon and ribavirin therapy can be determined from the patient's pretreatment viral load and HCV genotype. Clinical trial studies indicated that a decrease in HCV RNA levels of more than 2 log IU/mL at 4 weeks and/or 12 weeks of therapy is predictive of an increased chance of achieving a sustained virologic response (defined as undetectable HCV RNA levels in serum 6 months after completing antiviral therapy). Despite receiving longer duration of antiviral therapy (48 weeks versus 24 weeks), patients with chronic infection due to HCV genotypes 1 and 4 generally have less favorable sustained virologic response rates (40%-50%) than those infected with genotypes 2 and 3 (>80%). To determine the duration of treatment and monitor the response to anti-HCV therapy, HCV RNA levels in serum or plasma are typically measured at 0 (baseline), 4 (rapid virologic response, RVR), 8, and 12 (early virologic response: EVR) weeks of therapy, end-of-treatment (24, 28, or 48 weeks depending on HCV genotype and treatment response), and 24 weeks post-treatment (sustained virologic response: SVR).
The following algorithms are available in Special Instructions:
-Testing Algorithm for the Screening and Diagnosis of Hepatitis C
-Chronic Hepatitis C Treatment and Monitoring Algorithm: Interferon-Free Combination Therapy
Detection of acute hepatitis C virus (HCV) infection before the appearance of HCV antibodies in serum (ie, <2 months from exposure)
Detection and confirmation of chronic HCV infection
Quantification of HCV RNA in serum of patients with chronic HCV infection (HCV antibody-positive)
Monitoring disease progression in chronic HCV infection and/or response to anti-HCV therapy
This assay has a result range of 15 to 100,000,000 IU/mL (1.18 log to 8.00 log IU/mL) for quantification of hepatitis C virus (HCV) RNA in serum.
An "Undetected" result indicates that the HCV is absent in the patient’s serum specimen.
A result of "<15 IU/mL (<1.18 log IU/mL)" indicates that HCV RNA is detected, but the HCV RNA level present cannot be quantified accurately below this lower limit of quantification of this assay. When clinically indicated, follow-up testing with this assay is recommended in 1 to 2 months. To assess response-guided therapy eligibility, an "Undetected" result is required, and a result of "<15 IU/mL mL (<1.18 log IU/mL)" should not be considered equivalent to an "Undetected" result.
A quantitative result expressed in IU/mL and log IU/mL indicates the degree of active HCV viral replication in the patient. Monitoring HCV RNA levels over time is important to assess disease progression and/or monitoring a patient's response to anti-HCV therapy.
A result of ">100,000,000 IU/mL (>8.00 log IU/mL)" indicates the presence of active HCV viral replication, and the HCV RNA level present cannot be quantified accurately above this upper limit of quantification of this assay.
An "Inconclusive" result with the comment "Inconclusive" result. Submit a new specimen for testing if clinically indicated indicates that inhibitory substance(s) is/are present in the serum specimen tested. When clinically indicated, collection of a new serum specimen for retesting is recommended.
Except for immunocompromised patients or patients with suspected acute hepatitis, laboratory evaluation of hepatitis C virus (HCV) infection status should begin with HCV serologic testing, including testing for the presence of HCV antibodies (see Testing Algorithm for the Diagnosis of Hepatitis C in Special Instructions). A diagnosis of chronic HCV infection should not be based solely on the presence of detectable or quantifiable HCV RNA in a single serum specimen.
An "Undetected" HCV RNA test result with a "Reactive" HCV antibody screen result may be due to 1) a false-reactive HCV antibody screen result; 2) resolved or past HCV infection; or 3) transient low viremia (ie, episodic viral replication) of active HCV infection. To distinguish between the first 2 conditions, another HCV antibody test (eg, HCCAD / Hepatitis C Virus Antibody Screen for Cadaveric or Hemolyzed Specimens, Serum) can be requested. To distinguish between the latter 2 conditions, patients should be retested for HCV RNA in 1 to 2 months, as clinically indicated.
1. Ghany MG, Strader DB, Thomas DL, Seeff LB: Diagnosis, management, and treatment of hepatitis C–an update. Hepatology 2009;49:1335-1374
2. de Leuw P, Sarrazin C, Zeuzem S: How to use virological tools for the optimal management of chronic hepatitis C. Liver Int 2011;31 Suppl 1:3-12
3. Centers for Disease Control and Prevention: Testing for HCV infection–an update of guidance for clinicians and laboratorians. Mort Morbid Wkly Rpt 2013;62(18):362-365