Real-time PCR tests

Real-time PCR tests are faster and more cost-effective methods
that detect very low VL (10-15 IU/ml) (Vermehren 2008). Realtime
PCR can accurately quantify HCV RNA levels over a linear
range exceeding 6 logs (10 IU/mL to 100 million IU/mL) (Table
Patients’ monitoring during and after treatment | 33
2.2). Therefore, a single test result serves the purpose of both
quantitative and qualitative HCV NAT with similar sensitivity
(Ogawa 2010).
Table 2.2 – Currently available HCV RNA quantification methods*
Assay Manufacturer Method Conversion
Factor
(copies/mL)
Dynamic
Range
(IU/mL)
Cobas Taqman
HCV Test
Roche Molecular
Systems
Real time
PCR
3.4 43-69,000,000
Abbott Real-Time
PCR
Abbott Diagnostics Real time
PCR
3.4 12-100,000,000
LCx HCV RNA
Quantitative
Abbott Diagnostics RT-PCR 3.8 25-2,630,000
SuperQuant National Genetics
Institute
RT-PCR 3.4 30-1,470,000
Versant HCV RNA
3.0 Assay
Siemens Health
Care Diagnostics
bDNA 5.2 615-7,700,000
* According to data from Vermehren 2008 and Ghany 2009
Minimal residual viremia might be predictive of post-treatment
relapse (Matsuura 2009). Rules for treatment duration and early
discontinuation were mainly established with NAT assays with a
detection limit of 50 IU/ml. Lower detection limits (undetectable
VL defined as less than 15 IU/ml) did not significantly influence
the SVR rates after shortened treatment duration, for patients
with RVR (82% for G1 infected patients treated for 24 weeks and
95% for G2/3 infected patients treated for 16 weeks) (Sarrazin
2010).
The assay’s choice should be tailored to the dominant genotype
in the study population, as some assays have been reported to
substantially underestimate HCV RNA levels in certain
genotypes. The same assay should be used for all samples from a
single patient and, whenever possible, throughout the clinical
development program.