Comparison of three different diagnostic tests for HCV-RNA viral load: Cobas Amplicor Monitor HCV 2.0, Versant b-DNA HCV 3.0, and Cobas TaqMan HCV
Abstract number: 1733_1229
Ravanini P., Nicosia A., Crobu M., Grossini E., Quaglia V., Cagliano M., Cusaro C., Milano F., Caviglia F.
Objectives: The correct quantification of HCV-RNA viral load is an important parameter for the assessment and monitoring of antiviral therapy.
In this work, the possibility to obtain comparable results by different standardised tests for HCV-RNA viral load has been verified. To perform this aim we verified if there is an acceptable difference (<0.5 Log) among three different tests and if there are differences of quantification due to viral genotypes.
Methods: In the last years we performed two similar studies of comparison. The first one compared Bayer Versant HCV 3.0 and Roche Cobas Monitor HCV 2.0. 44 HCV-RNA positive samples of different genotype were collected and analysed by both methods between October 2001 and May 2002. A new study was performed between November 2005 and May 2006 on further 70 samples, comparing Bayer Versant HCV 3.0 and Roche Cobas TaqMan HCV.
Results: In the first study the median ratio between the results obtained by the two tests showed a value of 1.22 with a light overestimate of Cobas Monitor in comparison to Versant HCV. In the second study the median ratio was clearly higher: Cobas TaqMan showed an overestimate of 7.39 folds in comparison to Versant HCV. The cases with not acceptable differences (>0.5 Log) were 5/44 (11%) in the first study, and 60/70 (86%) in the second one.
The first study showed a good correspondence for genotype 1 (ratio 0.99), a light overestimate for genotypes 2 and 3 (ratio 1.86 and 1.46) and an underestimate for genotype 4 (ratio 0.79).
In the second study the only genotype with acceptable differences (<0.5 Log) was genotype 4 (ratio 2.0). The other genotypes showed poorer acceptability because of greater differences (genotype 1 ratio 7.87; genotype 2 ratio 6.30; genotype 3 ratio 13.11).
Conclusions: According to these data there is an important difference between the viral loads by Versant HCV and Cobas TaqMan. In the 86% of the cases these differences are not acceptable. The scattering of the results appears wider in the second study than in the first one. The comparison of different tests underwent a worsening.
Moreover there are great differences of quantification according to genotype. The only genotype with acceptable differences, in the second comparison, was genotype 4.
In our opinion the standardisation of molecular methods for HCV-RNA viral load testing is not yet concluded, and have to be resumed for new Real Time methods which seem to be not perfectly comparable with the other standardised methods.
|Session name:||European Society of Clinical Microbiology and Infectious Diseases|
|Location:||ICC, Munich, Germany|
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