New quantitative viral load assays for hepatitis C virus (HCV) with enhanced sensitivity are now available via LabFlorida.

The new test provides a lower limit of quantification (LLoQ) of 15 IU/mL and a lower limit of detection (LLoD) of 15 IU/mL.

Any result between 1 and 15 IU/mL will be reported as “detectable” but no value will be given. A “detectable” result (whether quantifiable or not) should be interpreted as evidence of continued presence of HCV RNA. This v2.0 assay enables more accurate assessments of response to antiviral therapy. Regular use of viral load assays for monitoring of patients is recommended in the 2009 Practice Guidelines and 2011 update from the American Association for the Study of Liver Diseases (AASLD).^1,2

For patients on direct-acting antivirals, treatment futility rules are as follows:

• Boceprevir: Discontinue treatment if HCV RNA >100 IU/mL at week 12, or detectable at any level at week 24.^2,3
• Telaprevir: Discontinue treatment if HCV RNA >1000 IU/mL at week 4 or week 12, or detectable at any level at week 24.^2,4

The 2009 guidelines emphasize the benefits of quantitative assays over qualitative assays: “With the recent availability of real time polymerase chain reaction (PCR)-based assays and transcription-mediated amplification (TMA) assays, with sensitivities of 10-50 IU/mL, there is no longer need for qualitative assays.” ¹

References

1. Ghany MC, Strader DB, Thomas DL, Seeff LB. Diagnosis, management, and treatment of hepatitis C: an update. AASLD Practice Guidelines. Hepatology. 2009;49(4):1335-1374.
2. Ghany MC, Nelson DR, Strader DB, Thomas DL, Seeff LB. An update on treatment of genotype 1 chronic hepatitis C virus infection: 2011 practice guideline by the American Association for the Study of Liver Diseases. Hepatology. 2011;54(4):1433-1444.
3. Victrelis [highlights of prescribing information]. Whitehouse Station, NJ: Merck & Co, Inc; May 2011.
4. Incivek [highlights of prescribing information]. Cambridge, MA: Vertex Pharmaceuticals Incorporated; May 2011.