Only limited data is available on the frequency and clinical significance of very low hepatitis C viremia (<600 IU/ml) determined by novel sensitive methods for HCV quantification.
We evaluated the new Abbott m2000 RealTime PCR assay in 3213 consecutive anti-HCV-positive sera as well as in 50 HCV-recovered patients with sustained virological response to standard antiviral therapy.
The assay showed a linear range between 10(1) IU/ml and 10(7) IU/ml for HCV genotypes 1-6. An HCV viremia below 600 IU/ml was detected more often with the m2000 RealTime PCR assay than with the Cobas Amplicor assay in viremic sera (7.1% versus 1.8%). Seventy-seven cases with HCV levels below 100 IU/ml not related to ongoing antiviral therapy were identified. An HCV-RNA of less than 12 IU/ml was found in nine of the 50 SVR patients. Two patients had a viral load of 34 IU/ml and 84 IU/ml, respectively, one of those showed persistently elevated ALT levels over a period of 5 years after the end of antiviral treatment.
An HCV viremia below 600 IU/ml can be detected in almost every 40th anti-HCV-positive sera using real-time PCR based assays. Low persisting HCV-RNA in patients after antiviral therapy may be associated with mild liver inflammation in single cases.
"Second, the duplex primer/probe assay can estimate the virus levels accurately. There are many reports about the underestimation of virus load by singleplex primer/probe assays [12,21,22,29,31]. For example, some patients with very low HCV viraemia may yield a negative result by the CAP/CTM assay . "
[Show abstract][Hide abstract] ABSTRACT: The hepatitis C virus (HCV) genome is extremely heterogeneous. Several HCV infections can not be detected using currently available commercial assays, probably because of mismatches between the template and primers/probes. By aligning the HCV sequences, we developed a duplex real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay using 2 sets of primers/probes and a specific armored RNA as internal control. The 2 detection probes were labelled with the same fluorophore, namely, 6-carboxyfluorescein (FAM), at the 5' end; these probes could mutually combine, improving the power of the test.
The limit of detection of the duplex primer/probe assay was 38.99 IU/ml. The sensitivity of the assay improved significantly, while the specificity was not affected. All HCV genotypes in the HCV RNA Genotype Panel for Nucleic Acid Amplification Techniques could be detected. In the testing of 109 serum samples, the performance of the duplex real-time RT-PCR assay was identical to that of the COBAS AmpliPrep (CAP)/COBAS TaqMan (CTM) assay and superior to 2 commercial HCV assay kits.
The duplex real-time RT-PCR assay is an efficient and effective viral assay. It is comparable with the CAP/CTM assay with regard to the power of the test and is appropriate for blood-donor screening and laboratory diagnosis of HCV infection.
[Show abstract][Hide abstract] ABSTRACT: The introduction of commercially available quantitative HIV-1 RNA detection methods at the end of the last century has had a significant impact on the management of patients requiring treatment. Similarly for hepatitis C virus (HCV), clinical decision-making with respect to initiation and prolonging therapy is largely based on data from viral load assays. The methods developed in the early 1990s and further improved since then still have significant drawbacks. For example, they are labor intensive, have a small dynamic range and are contamination sensitive. The development of real-time detection techniques for reverse transcription PCR has in part solved these problems. In the present review the advantages and disadvantages of the recently marketed Abbott Realtime HCV and HIV-1 viral load assays relative to their competitors will be discussed.
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