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COMPARISON OF PLASMA VIRUS LOADS AMONG INDIVIDUALS INFECTED WITH
HEPATITIS C VIRUS (HCV) GENOTYPE-1, GENOTYPE-2, AND GENOTYPE-3 BY
QUANTIPLEX HCV RNA ASSAY VERSION-1 AND VERSION-2, ROCHE MONITOR
ASSAY, AND AN IN-HOUSE LIMITING DILUTION METHOD
The accuracy of different methods for the quantitation of
hepatitis C virus in plasma was measured with samples from
individuals infected with different genotypes and by using RNA
transcripts of predetermined concentrations, Highly reproducible
results were observed upon repeat testing of samples by both the
original version of the Chiron branched-DNA (bDNA) assay
(Quantiplex RNA assay; bDNA- 1) and the currently available version
(Quantiplex HCV RNA 2.0 assay; bDNA-2), A greater variability was
observed in the Roche Monitor assay (correlation coefficient of
0.537, compared with 0.942 and 0.964 for the bDNA-1 and bDNA-2
assays, respectively), Significant differences in the efficiency of
detection of genotypes 1, 2, and 3 were observed for the bDNA-1 and
Roche Monitor assays, whereas the bDNA-2 assay and nested PCR at
limiting dilution were able to quantify genotypes with equal
sensitivity, By quantifying RNA transcripts of different genotypes,
the sensitivities of the Roche Monitor assay for sequences of the
type 2 and type 3 transcripts were estimated to be 11 and 8% of
those achieved for genotype 1, When correction factors based upon
these results and those from quantitation of circulating viral RNA
sequences in samples from blood donors were used, the
genotype-specific differences in virus load in samples from blood
donors were no longer observed, consistent with previous studies
with corrected values from the bDNA-1 assay, These results suggest
that many of the previous studies evaluating the effect of genotype
and virus load on the response to interferon using methods such as
the Roche Monitor assay and other competitive PCR methods require
reinterpretation. Differences in efficiency of quantitation should
be taken into account in future investigations of the relationship
between genotype and virus load.
Author: P SIMMONDS, UNIV EDINBURGH, DEPT MED MICROBIOL,
TEVIOT PL, EDINBURGH EH8 9AG MIDLOTHIAN
Source: JOURNAL OF CLINICAL MICROBIOLOGY 1997
JAN;35(1):187-192
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