Hepatitis C virus infection and disease. Diagnostic problems

Performance of the COBAS AMPLICOR HCV MONITOR test, version 2.0, an automated reverse transcription-PCR quantitative system for hepatitis C virus load determination

A clinical evaluation of an automated quantitative PCR assay, the COBAS AMPLICOR HCV MONITOR test, version 2.0 (v2.0), was carried out to assess the performance of this test in comparison with that of the previous, manual version, the AMPLICOR HCV MONITOR test, and with that of nested PCR. Serial dilutions of serum samples infected with genotype 1b, 2a, or 3, as well as synthetic RNA transcripts and serum samples derived from 87 patients with chronic hepatitis C and infected with genotype 1a, 1b, 2a, 2b, 3a, 3b, 4, or 5, were analyzed to determine the ability of the system to efficiently quantify various hepatitis C virus (HCV) genotypes. These experiments showed that the COBAS AMPLICOR HCV MONITOR test, v2.0, has mean intra-assay, interassay, and interoperator coefficients of variation that range from 22 to 34.5% and a 3-logarithm dynamic range, which spans from 10(3) to 10(6) copies/ml. Compared to the previous, manual version of the test, the COBAS AMPLICOR HCV MONITOR test, v2.0, showed an improved efficacy for all genotypes, especially genotypes 2, 3, and 4, whose estimated concentrations were on average 1 logarithm higher. When used to monitor patients under treatment, however, both versions showed the same patterns of viremia, indicating that the COBAS AMPLICOR HCV MONITOR test, v2.0, and the AMPLICOR HCV MONITOR test were equally effective at detecting relative viremia changes in serial samples. As expected, the automated test was less sensitive than nested PCR; among specimens from a cohort of patients treated with interferon, nested PCR identified three more viremic specimens, which probably contained very low concentrations of HCV RNA.

Multicenter evaluation of the COBAS AMPLICOR HCV assay, an integrated PCR system for rapid detection of hepatitis C virus RNA in the diagnostic laboratory

The benefits shown by the recent introduction of PCR for the in vitro diagnosis of hepatitis C virus (HCV) infection has prompted the development of standardized, ready-to-use assays that can be implemented in routine clinical laboratories. We have evaluated the clinical performance of COBAS AMPLICOR HCV (COBAS), the first instrument system that allows the automation of HCV RNA amplification and detection, to determine its performance in the routine laboratory setting. More than 2,000 specimens collected at five centers were analyzed in parallel by the COBAS and the manual AMPLICOR HCV (AMPLICOR) tests, and the results were compared with the results for biochemical and serological markers of HCV. In this study the two PCR systems showed the same accuracy, with a concordance rate of 99.8%. As expected, the correlation between serology and PCR was not absolute because the presence of anti-HCV antibodies may be associated with a latent or past infection. On the other hand, if the presence of confirmed anti-HCV antibodies and elevated alanine aminotransferase levels are taken as the "gold standard," indicating an active, ongoing infection, the COBAS and AMPLICOR tests show high and comparable sensitivities (100%) and specificities (98%), with positive and negative predictive values of 100 and 97%, respectively. During the study no false-positive reactions were detected. The use of an internal control allowed the identification of inhibitory substances that prevented amplification for 0.3 and 0.4% of samples tested by the COBAS and AMPLICOR tests, respectively. Compared to the manual system, the COBAS system allowed a significant reduction of hands-on time and could improve the overall laboratory work flow. In conclusion, these results support the use of the COBAS and AMPLICOR tests for the molecular diagnosis of active HCV infections.

Quantitative detection of hepatitis C virus RNA in the serum of patients with chronic hepatitis C treated with interferon: a pilot study

BACKGROUND

It is not known whether the measurement of serum hepatitis C virus (HCV) RNA by reverse transcription polymerase chain reaction (RT-PCR) could improve the management of patients with chronic hepatitis C being treated with interferon.

OBJECTIVES

We analysed, in a pilot study, the relations between the variations of HCV-RNA and alanine aminotransferase (ALT) serum levels in 18 anti-HCV positive patients treated with interferon.

STUDY DESIGN

Serum HCV-RNA was measured, using a non competitive coamplification assay (Amplicor HCV Monitor), before (at 3, 2 and 1 months and baseline), during (first, third and sixth month) and after treatment for at least 8 months (range 8-17 months). HCV-RNA levels fluctuations were correlated with those of ALT and treatment outcome. According to the ALT pattern, four patients were non responders, seven partial responders, four relapsers and two long term responders.

RESULTS

The median and mean baseline HCV-RNA levels were significantly different in patients infected by HCV type 1, 2 and 3, being 248,449, 235,506; 4170, 17,866 and 22,315, 79,273 molecules per ml, respectively (P < 0.0001). We did not find any significant difference between median and mean baseline viremia of responders and non responders. After 1 month of treatment viremia was below the sensitivity levels of the assay in 77.7% (14/18) of the patients who normalized ALT, at least temporarily. On the contrary, HCV-RNA remained detectable in non responders.

CONCLUSIONS

Our data suggest that HCV-RNA detection using Amplicor Monitor at the first month of treatment can be useful to identify non responders, avoiding three additional months of treatment as would be required by ALT monitoring alone. During the post-treatment follow-up, persistence of undetectable HCV-RNA and normal ALT levels helps to identify long term responders from patients with the risk of relapse in spite of biochemical remission.

Clinical significance of hepatitis C viral RNA status and its correlation to antibodies to structural HCV antigens in anti-HCV reactive patients with normal liver tests

Extensive serological testing and HCV RNA determination by RT-PCR was performed in serum, PBMCs, and liver tissue in thirteen anti-HCV reactive patients with persistently normal liver tests. Absolute concordance in the status of HCV RNA between serum, PBMCs, and liver was noted. Five patients were HCV RNA positive but only three had mild histological changes. Eight patients were HCV RNA negative in all three sites and had virtually normal liver histology. Patterns of reactivity in RIBA 2.0 strip immunoblot assay did not differentiate viremic from nonviremic patients. ELISA testing using multiple individual HCV recombinant antigens from the structural and non-structural regions of HCV demonstrated mean antibody titers to the structural antigens, in particular HCV E2 antibodies, to be significantly lower in HCV RNA negative patients. The status of HCV RNA in the serum appears to infer the status of HCV RNA in the liver and PBMCs in patients with persistently normal liver tests. Patients with persistently normal liver tests and undetectable HCV RNA have probably spontaneously cleared HCV infection.

Clinical evaluation of a single reaction, diagnostic polymerase chain reaction assay for the detection of hepatitis C virus RNA

BACKGROUND/AIMS

In the past few years the detection of HCV-RNA by polymerase chain reaction has become a well-established diagnostic tool for patients with chronic hepatitis C. However, the lack of reproducible results between laboratories and the relatively high proportion of false-positive results, has indicated the need for a standardized and reliable polymerase chain reaction assay. In the present study we have analyzed the performance of a commercial, HCV-RNA polymerase chain reaction assay based on a single, combined reverse transcription and amplification reaction and on the use of Uracil-N-glycosilase to prevent carry-over contamination (Amplicor HCV, Roche Molecular Systems).

METHODS

In this assay the amplification products are detected in microwell plates using biotinylated primer and the HRP avidin colorimetric system. Serum samples collected from 446 patients, including 181 with chronic active hepatitis C, 50 with autoimmune chronic hepatitis, 117 in hemodialysis, 30 asymptomatic carriers of anti-HCV and 68 with indeterminate serology (RIBA indeterminate results), as well as from 121 controls were tested with the commercial, single-step assay and with nested polymerase chain reaction. Both techniques use primers located within the 5' non-coding region of the HCV genome.

RESULTS

In all cases a good concordance was observed between the commercial, single-step assay and nested polymerase chain reaction which, for patients with chronic active hepatitis, showed a sensitivity and specificity of 100% and 99.3% for the former and of 98.8% and 100% for the latter, when compared to clinical diagnosis taken as the gold standard. Most of the 11 discordant samples were seen in the group of RIBA-indeterminate cases and in patients with chronic active hepatitis C. Further analysis of these cases, based on repeat testing and clinical data showed that 64% and 36% of the discrepancies were due, respectively, to nested polymerase chain reaction and Amplicor inconsistent reactions. In hemodialyzed patients, patients with autoimmune hepatitis and asymptomatic carriers of anti-HCV, both assays produced results which were consistent with the clinical diagnosis. In the former group, polymerase chain reaction was able to identify the presence of active viral replication in some antibody negative samples.

CONCLUSIONS

Taken together, these results indicate that the commercial, single-step polymerase chain reaction assay has the same clinical sensitivity and specificity as nested polymerase chain reaction and that, because of its simplified procedures and fast turn-around time, it may be a valuable test for routine diagnostic applications.

[Study of HCV infection and viremia in patients with posttransfusion hepatitis in China]

One hundred and sixty-nine patients with posttransfusion hepatitis (PTH) were investigated for etiology with serological and PCR methods. Our result showed that HCV was the major causative agent of PTH in this study. A part of patients (24/169) were also HBV markers positive. Three patients were negative for all detected viral markers, looking forwards to progressive study. Anti-HCV was detectable from 7 days to one year after onsetting of clinical symptoms, average time 54.62 days. HCV RNA could be detected in early time of HCV infection ( 6 to 20 days later), average time 8.72 days. A follow-up study of 84 patients showed that all patients remained anti-HCV positive during the observation for 1.5 -- 3 years, but their HCV viremia had three forms: transient, persistent or intermittent. The interaction between HCV and HBV by their superinfection was unknown, awaiting further study.

Long term follow-up and patterns of response of ALT in patients with chronic hepatitis NANB/C treated with recombinant interferon-alpha

The response to interferon treatment in chronic hepatitis NANB/C has usually been classified as complete, partial or absent, according to the behavior of serum alanine aminotransferase (ALT). However, a more detailed observation of the enzymatic activity has shown that the patterns may be more complex. The aim of this study was to describe the long term follow-up and patterns of ALT response in patients with chronic hepatitis NANB/C treated with recombinant interferon-alpha. A follow-up of 6 months or more after interferon-alpha was achieved in 44 patients. We have classified the serum ALT responses into six patterns and the observed frequencies were as follows: I. Long term response = 9 (20.5%); II. Normalization followed by persistent relapse after IFN = 7 (15.9%); III. Normalization with transient relapse = 5 (11.9%); IV. Temporary normalization and relapse during IFN = 4 (9.1%); V. Partial response (more than 50% of ALT decrease) = 7 (15.9%); VI. No response = 12 (27.3%). In conclusion, ALT patterns vary widely during and after IFN treatment and can be classified in at least 6 types.

Pathology of hepatitis C virus infection

This paper reviews our current knowledge of hepatitis C virus, its structure, epidemiology and pathological effects in man. The histopathological features of acute and chronic hepatitis due to hepatitis C virus are detailed and illustrated. The possible pathogenetic mechanisms involved in the liver injury are outlined and the significance of genotypic subtypes of the virus and of host genetic predisposition in relation to the liver injury and the response to therapy are summarized.

Quantitation of HCV-replication using one-step competitive reverse transcription-polymerase chain reaction and a solid phase, colorimetric detection method

A solid phase assay for the colorimetric detection of competitively amplified HCV-cDNA has been established and used to investigate clinical samples from patients with chronic hepatitis. The assay is based on the reduction in the amplification of an hepatitis C virus-related competitor molecule by wild-type hepatitis C virus during polymerase chain reaction. The internal standard contains a lac operator sequence, allowing the amount of amplified competitor to be determined using a lac I-repressor/beta-galactosidase fusion protein. The reduction in the amplification of competitor is dependent upon the concentration of HCV-RNA in the original sample. External hepatitis C virus wild-type standards are used to calibrate each concurrently tested set of patients. We present and discuss the potential benefit, but also the limitations of this new approach for quantifying hepatitis C virus viremia. In 47 serum samples from 28 patients with chronic hepatitis C virus infection, including five repeatedly tested alpha HCV positive patients under interferon therapy, viral titer was determined. Sera from nine healthy blood donors served as controls. The sensitivity and specificity of this procedure are identical to those of conventional nested polymerase chain reaction. As both internal and external standards are used in every assay and final detection of amplicons can be carried out in microtiter plates, this reliable and time-saving test system may be routinely applied for monitoring antiviral treatment or for studying the relation of plus- and minus-stranded HCV-RNA in infected tissues.