Real-time polymerase chain reaction and HCV RNA quantification: comparison of Cobas Ampliprep-Cobas TaqMan and branched DNA technology
Abstract number: p653
Allice T., Gabella S., Varetto S., Pittaluga F., Smedile A., Cerutti F., Ghisetti V.
Management of therapy for hepatitis C virus (HCV) infection is based on quantitative measurement of HCV RNA and the decision of treatment discontinuation on the basis of a 2 log decline at week 12 is a widely accepted rule.
Aims and methods:
In the present study, we evaluated the performance of the completely automated system Cobas Ampliprep-Cobas TaqMan (CAP/CTM, Roche Diagnostics, Branchburg, NJ) for HCV RNA quantification in clinical serum specimens. CAP/CTM is a real time Polymerase Chain assay that relies on an automated nucleic acid extraction from 1050 ml of serum followed by RNA capture using magnetic particles, purification and elution. The system has a reported lower detection limit of 15 IU/ml and a dynamic range from 43 to 6.9E7 IU/ml. CAP/CTM results were compared for quantification of HCV genotype 14 with those from a signal amplification assay based on the branched DNA (bDNA) technology, the Versant Quantitative 3.0 (Bayer Diagnostic, Tarrytown, NY, detection limit 615 IU/ml and dynamic range from 1185 to 1.5E7 IU/ml).
Sixty-three clinical specimens from patients with HCV infection were studied. The two assays were concordant (r = 0.85) with a mean ± SD interassay difference of -0.06 ± 0.8 log IU/ml. However, when the CAP/CTM values were analyzed for genotype, the mean ± SD interassay difference with bDNA were as follows: genotype 1 (n = 26), 0.3 ± 0.4, genotype 2a/2c (n = 12), 0.1 ± 0.2; genotype 3a (n = 18), -0.6 ± 1.4; genotype 4 (n = 7), -0.4 ± 0.7 log IU/ml, thus appearing that values obtained from CAP/CTM were in general 0.5 log lower than those from the bDNA for genotype 3a and 4. CAP/CTM detected HCV RNA in 8 (62%) out of 13 samples below 615 IU/ml with the bDNA (CAP/CTM levels from 1.4 to 3.5 log). Six out of the 8 CAP/CTM+/bDNA-specimens were from genotype 1 infected patients.
CAP/CTM showed a good correlation with bDNA with a better sensitivity that is crucial for the management of anti-HCV therapy, particularly for genotype 1. However, it seem that CAP/CTM underestimates HCV RNA levels in genotype 3 and 4 and this is clinically relevant as decisions during the clinical management of patients are based on measurements of HCV RNA levels and HCV RNA decline in patients on anti-HCV therapy.
|Session name:||XXIst ISTH Congress|
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