《2009AASLD丙型肝炎診斷，管理和治療：更新》內(nèi)容預(yù)覽

Genotyping Assays. Genotyping is useful in epide-miological studies and in clinical management for pre-dicting the likelihood of response and determining theoptimal duration of therapy. The hepatitis C virus can beclassi??ed into at least 6 major genotypes (genotypes 1 to6) based on a sequence divergence of 30% among iso-lates.46Genotype 1 (subtypes 1a and 1b) is the most com-mon in the U.S., followed by genotypes 2 and 3. Lesscommon genotypes (genotypes 4-6) are beginning to beobserved more frequently because of the growing culturaldiversity within the United States.47Several commercialassays are available to determine HCV genotypes usingdirect sequence analysis of the 5 non-coding region, thatinclude Trugene 5 NC HCV Genotyping kit (SiemensHealthcare Diagnostics Division, Tarrytown, NY), re-verse hybridization analysis using genotype speci??c oligo-nucleotide probes located in the 5 non-coding region,INNO-LiPa HCV II, (Innogenetics, Ghent, Belgium),and Versant HCV Genotyping Assay 2.0 (SiemensHealthcare Diagnostics Division, Tarrytown, NY). In-correct typing among the major genotypes is rare ( 3%)and mixed genotypes occur but are uncommon. Occa-sionally ( 5%), tested samples cannot be genotyped.This usually results from low viral levels, issues with thePCR ampli??cation step of the assay, or extreme nucleo-tide variability within the HCV genome.
Diagnosis of Acute and Chronic HCVInfection and Interpretation of AssaysThe diagnosis of acute or chronic HCV infection gen-erally requires testing of serum for both antibody to HCV(anti-HCV) and for HCV RNA. A sensitive quantitativeHCV RNA assay is recommended for diagnosis because italso provides information on the level of virus which ishelpful in management.

The differentiation of acute from chronic HCV infec-tion depends on the clinical presentation: namely thepresence of symptoms or jaundice, and whether or notthere was a prior history of ALT elevation and its dura-tion. After acute exposure, HCV RNA is usually detectedin serum before antibody; HCV RNA can be identi??ed asearly as 2 weeks following exposure whereas anti-HCV isgenerally not detectable before 8-12 weeks. These twomarkers of HCV infection may be present in varying per-mutations, requiring careful analysis for interpretation(Table 6).

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