Reliability of polymerase chain reaction for detection of hepatitis C virus

The metabolic fingerprint of chronic hepatitis C progression: Metabolome shifts and cutting-edge diagnostic options

Hepatitis C virus infection causes chronic diseases such as cirrhosis and hepatocellular carcinoma. Metabolomics research has been shown to be linked to pathophysiologic pathways in liver illnesses. The aim of this study was to investigate the serum metabolic profile of patients with chronic hepatitis C (CHC) infection and to identify underlying mechanisms as well as potential biomarkers associated with the disease. Nuclear magnetic resonance (NMR) was used to evaluate the sera of 83 patients with CHC virus and 52 healthy control volunteers (NMR). Then, multivariate statistical analysis was used to find distinguishing metabolites between the two groups. Sixteen out of 40 metabolites including include 3-HB, betaine, carnitine, creatinine, fucose, glutamine, glycerol, isopropanol, lysine, mannose, methanol, methionine, ornithine, proline, serine, and valine-were shown to be significantly different between the CHC and normal control (NC) groups (variable importance in projection >1 and p < 0.05). All the metabolic perturbations in this disease are associated with pathways of Glycine, serine, and threonine metabolism, glycerolipid metabolism, arginine and proline metabolism, aminoacyl-tRNA biosynthesis, cysteine and methionine metabolism, alanine, aspartate, and glutamate metabolism. Multivariate statistical analysis constructed using these expressed metabolites showed CHC patients can be discriminated from NCs with high sensitivity (90%) and specificity (99%). The metabolomics approach may expand the diagnostic armamentarium for patients with CHC while contributing to a comprehensive understanding of disease mechanisms.

Standardization of NAT for Blood-Borne Pathogens

Assays based on nucleic acid amplification technology (NAT) are increasingly used for screening of blood and for diagnosis or monitoring of patients. Both regulatory requirements for blood screening and international recommendations for the treatment of patients are based on common reference materials available globally for the standardization of NAT assays. World Health Organization International Standards (WHO ISs) and International Reference Panels (WHO IRPs) are primary reference materials. The characterization and manufacture of WHO reference materials as well as their evaluation is performed on behalf of the WHO by collaborating centers; their establishment is decided upon by the WHO Expert Committee on Biological Standardization (ECBS). The potency of the first WHO IS is defined by the 'international unit' (IU) which should be maintained upon replacement of the IS. The IU, unlike copy number or genome equivalent, is defined by the IS with a physical existence, is available worldwide, and allows traceability and comparability of results. The anticipated use of WHO ISs is the calibration of secondary standards or the validation of essential assay features, e.g. limit of detection.

What is the meaning of a nonresolved viral nucleic acid test-reactive minipool?

BACKGROUND

This study aimed at analyzing the prevalence of hepatitis B virus (HBV) DNA among hepatitis B surface antigen (HBsAg)-negative donations by cobas TaqScreen MPX test (Roche Molecular Systems) and discussing the meaning of a reactive minipool (MP) that does not resolve to an individual donation (ID)-reactive result.

STUDY DESIGN AND METHODS

Nucleic acid amplification testing (NAT) was performed in 12 Chinese blood centers on 826,044 serologic negative donations in MPs of six. MP-reactive pools that were resolved to ID-reactive donations were confirmed by Roche TaqMan viral load assays. Antibody to hepatitis B surface antigen and antibody to hepatitis B core antigen (anti-HBc) results were also analyzed. Cycle threshold (Ct) values of reactive MPs were analyzed in relation to the probability of pool resolution.

RESULTS

A total of 1267 of 137,674 pools were reactive, of which 839 donations were reactive by ID-NAT. The MP6 HBV NAT-yield rate lay between 1 in 1600 and 1 in 1000. At MP Ct values equal or below 37, the probability of pool resolution was approximately 80%. The prevalence of anti-HBc in ID-reactive donations was 81%. The proportion of reactive pools that could not be resolved was 36%. The prevalence of anti-HBc in donations implicated in nonresolved MPs was significantly higher than those in nonreactive MPs (48% vs. 37%, p = 0.016).

CONCLUSION

The anti-HBc data suggest that approximately 10% of nonresolved MPs contain HBV DNA from a low-viral-load occult carrier. We consider ID-NAT resolution testing in duplicate to minimize HBV transmission risk associated with transfusing nonreactive donations implicated in reactive MPs.

Usefulness of liver biopsy in anti-hepatitis C virus antibody-positive and hepatitis C virus RNA-negative kidney transplant recipients

BACKGROUND

Some guidelines recommend a liver biopsy to all anti-hepatitis C virus (HCV) antibody-positive kidney transplant (KT) recipients. However, in the case of HCV RNA-negative KT recipients, the benefit of a liver biopsy is unclear. We examined the usefulness of a liver biopsy for anti-HCV antibody-positive and HCV RNA-negative patients by analyzing the hepatic histologic findings and clinical outcomes.

METHODS

A total of 30 anti-HCV antibody-positive patients who underwent liver biopsy before KT at Asan Medical Center were retrospectively recruited. The patients were divided into two groups based on HCV RNA positivity: 17 patients were positive and 13 patients were negative. Histologic evidence of hepatic inflammation and fibrosis was assessed using the METAVIR score, and clinical outcomes, including mortality, graft loss, and progression of liver disease, were compared.

RESULTS

The mean histologic activity scores for inflammation and fibrosis for the HCV RNA-positive and HCV RNA-negative groups were significantly different (inflammation score 1.11 ± 0.85 vs. 0.46 ± 0.51; P=0.01 and fibrosis score 1.05 ± 1.24 vs. 0.15 ± 0.37; P=0.01, respectively). The overall rates of mortality and graft loss were not significantly different between the two groups. Progression of liver disease was noted in the HCV RNA-positive group only.

CONCLUSION

The HCV RNA-negative group showed no evidence of liver disease progression. Neither did they show any histologic evidence of liver inflammation and fibrosis before KT. Therefore, it appears that liver biopsy is not necessary in anti-HCV antibody-positive and HCV RNA-negative KT recipients.

A novel double antibody sandwich-lateral flow immunoassay for the rapid and simple detection of hepatitis C virus

The objective of this study was to screen for antigens of the hepatitis C virus (HCV) to establish a new double antibody sandwich-lateral flow immunoassay (DAS-LFIA) method for testing the presence of anti-HCV antibodies in human serum or plasma. A series of different recombinant HCV proteins in Escherichia coli cells were constructed, expressed, purified and the new DAS-LFIA strip was developed. The sensitivity and specificity of new the DAS-LFIA strip were evaluated by detecting 23 HCV-positive sera, a set of quality control references for anti-HCV detection that contain known amounts of anti-HCV antibodies, and 8 HCV-negative sera. A total of 300 clinical serum samples was examined by both the new DAS-LFIA strip and enzyme-linked immunosorbent assay (ELISA). Data were analyzed using SPSS 11.5 software. The sensitivity and specificity of the new DAS-LFIA strip were 100%. The lowest test line of the HCV DAS-LFIA strips was 2 NCU/ml. Additionally, the concordance between the new DAS-LFIA strip and ELISA methods was 94.33%. In conclusion, our new testing method is rapid, simple, sensitive and specifically detects the presence of anti-HCV antibodies in human serum or plasma. Therefore, it may be used for monitoring HCV.

Hepatitis C virus infection diagnosis using metabonomics

Metabonomics based on nuclear magnetic resonance (NMR) can reveal the profile of endogenous metabolites of low molecular weight in biofluids related to disease. The profile is identified a 'metabolic fingerprint' like from the pathological process, why this metabonomics has been used as a diagnostic method. The aim of the present study was to apply metabonomics to identify patients infected with the hepatitis C virus (HCV) through an analysis of ¹H NMR spectra of urine samples associated with multivariate statistical methods. A pilot study was carried out for the diagnostic test evaluation, involving two groups: (i) 34 patients positive for anti-HCV and HCV-RNA and negative for anti-HBc (disease group); and (ii) 32 individuals positive for anti-HBc and negative for HBsAg and anti-HCV. The urine samples were analyzed through ¹H NMR, applying principal component analysis and discriminant analysis for classification. The metabonomics model was capable of identifying 32 of the 34 patients in the disease group as positive and 31 of the 32 individuals in the control group as negative, demonstrating 94% sensitivity and specificity of 97% as well as positive and negative predictive values of 97% and 94%, respectively, and 95% accuracy (P < 0.001). In conclusion, the metabonomics model based on ¹H NMR spectra of urine samples in this preliminary study discriminated patients with HCV infection with high sensitivity and specificity, thereby demonstrating this model to be a potential tool for use in medical practice in the near future.

International standards and reference materials for quantitative molecular infectious disease testing

The utility of quantitative molecular diagnostics for patient management depends on the ability to relate patient results to prior results or to absolute values in clinical practice guidelines. To do this, those results need to be comparable across time and methods, either by producing the same value across methods and test versions or by using reliable and stable conversions. Universally available standards and reference materials specific to quantitative molecular technologies are critical to this process but are few in number. This review describes recent history in the establishment of international standards for nucleic acid test development, organizations involved in current efforts, and future issues and initiatives.

Molecular Diagnostics and Comparative Genomics in Clinical Microbiology

Initially, the availability of molecular diagnostics was considered a panacea, but replacement of conventional tests for detection and identification of microorganisms by molecular procedures eventually gathered momentum. This chapter describes current state-of-the-art molecular diagnostics and comparative genomics in medical microbiology to provide an understanding of infectious disease over the coming years. Nucleic acid-based tests are being introduced with increasing speed into routine clinical microbiology laboratories. Some of the problems remaining to be solved prior to general acceptance of nucleic acid-mediated detection and identification of microbial pathogens are reviewed. Historic objections are slowly being taken apart, and an accelerated introduction of molecular diagnostics is being pursued in many cases. Clear improvement in clinical testing is achieved by introducing molecular tests. Therefore, swift introduction of such tests into clinical practice is important to be pursued. Several PCR tests show increased sensitivity, excellent specificity, and cost effectiveness highlighting the success of the novel applications in the field of bacterial infections. Finally, some of the problems remaining to be solved prior to general acceptation of nucleic acid-mediated detection and identification of microbial pathogens are also reviewed.

Molecular and contextual markers of hepatitis C virus and drug abuse

The spread of hepatitis C virus (HCV) infection involves a complex interplay of social risks, and molecular factors of both virus and host. Injection drug abuse is the most powerful risk factor for HCV infection, followed by sexual transmission and additional non-injection drug abuse factors such as co-infection with other viruses and barriers to treatment. It is clearly important to understand the wider context in which the factors related to HCV infection occur. This understanding is required for a comprehensive approach leading to the successful prevention, diagnosis, and treatment of HCV. An additional consideration is that current treatments and advanced molecular methods are generally unavailable to socially disadvantaged patients. Thus, the recognition of behavioral/social, viral, and host factors as components of an integrated approach to HCV is important to help this vulnerable group. Equally important, this approach is key to the development of personalized patient treatment - a significant goal in global healthcare. In this review, we discuss recent findings concerning the impact of drug abuse, epidemiology, social behavior, virology, immunopathology, and genetics on HCV infection and the course of disease.

Consistency of quantitation of HCV genotype 4 from egypt across three HCV-RNA amplification assays

Different quantitative assays for HCV-RNA are available that report test results in International Units (IU)/ml based on the WHO International Standard. Thus, assays have been calibrated with standard material containing HCV genotype 1, so the consistency of quantitation might differ between assays for other HCV genotypes. Three commercial HCV nucleic acid amplification techniques (HCV-NAT) were compared for quantitation consistency of genotype 4 and 1 specimens from an Egyptian blood donor panel (n = 92). Consistency of quantitation between HCV-NATs was higher for genotype 1 than for genotype 4. Most quantitative results reported by the assays were in the same range, but some genotype 4 samples were missed by two of the assays. The Abbott assay showed higher concentrations for genotype 4 than the two Roche assays. Follow-up investigations of individuals should use the same assay unless another assay has been validated properly. Standardization of HCV-NAT assays remains an issue.

Comparison of performance characteristics of three real-time reverse transcription-PCR test systems for detection and quantification of hepatitis C virus

We evaluated the performance characteristics of three real-time reverse transcription-PCR test systems for detection and quantification of hepatitis C virus (HCV) and performed a direct comparison of the systems on the same clinical specimens. Commercial HCV panels (genotype 1b) were used to evaluate linear range, sensitivity, and precision. The Roche COBAS TaqMan HCV test for research use only (RUO) with samples processed on the MagNA Pure LC instrument (Roche RUO-MPLC) and Abbott analyte-specific reagents (ASR) with QIAGEN sample processing (Abbott ASR-Q) showed a sensitivity of 1.0 log(10) IU/ml with a linear dynamic range of 1.0 to 7.0 log(10) IU/ml. The Roche ASR in combination with the High Pure system (Roche ASR-HP) showed a sensitivity of 1.4 log(10) IU/ml with a linear dynamic range of 2.0 to 7.0 log(10) IU/ml. All of the systems showed acceptable reproducibility, the Abbott ASR-Q being the most reproducible of the three systems. Seventy-six clinical specimens (50 with detectable levels of HCV RNA and various titers and genotypes) were tested, and results were compared to those of the COBAS Amplicor HCV Monitor v2.0. Good correlation was obtained for the Roche RUO-MPLC and Abbott ASR-Q (R(2) = 0.84 and R(2) = 0.93, respectively), with better agreement for the Abbott ASR-Q. However, correlation (R(2) = 0.79) and agreement were poor for Roche ASR-HP, with bias relative to concentration and genotype. Roche ASR-HP underestimated HCV RNA for genotypes 3 and 4 as much as 2.19 log(10) IU/ml. Our study demonstrates that Roche RUO-MPLC and Abbott ASR-Q provided acceptable results and agreed sufficiently with the COBAS Amplicor HCV Monitor v2.0.

Two quality control exercises involving nucleic acid amplification methods for detection of Mycoplasma pneumoniae and Chlamydophila pneumoniae and carried out 2 years apart (in 2002 and 2004)

The quality performance of laboratories for the detection of Mycoplasma pneumoniae and Chlamydophila pneumoniae by two quality control (QC) exercises with a 2-year interval was investigated. For the 2002 QC exercise, specimens were spiked with M. pneumoniae at concentrations of 5,000, 500, 50, and 0 color-changing units (CCU)/100 microl. The limit of detectability was 50 CCU/100 microl. Therefore, this concentration was omitted from the 2004 panel and was excluded from the analysis. In 2002, 2 out of 12 participants obtained 100% correct results, 2 out of 12 produced false-positive results, and 10 out of 12 had between 0 out of 9 and 8 out of 9 correct positive results. In 2004, correct results were obtained in 15 out of 18 tests, and no false-positive results were reported. In 2002, specimens were spiked with C. pneumoniae at concentrations of 490, 49, 4.9, and 0 inclusion-forming units/100 microl (IFU/100 microl). In the 2004 panel, samples spiked with a lower dilution of 0.49 IFU/100 microl were added to the panel. For the C. pneumoniae QC, correct results were produced in 12 out of 16 and 13 out of 18 tests in 2002 and in 2004, respectively. Both multiplex PCR and nucleic acid sequence-based amplification (NASBA) formats scored a smaller number of samples positive than the monoplex reactions.

Benefit of hepatitis C virus core antigen assay in prediction of therapeutic response to interferon and ribavirin combination therapy

A highly sensitive second-generation hepatitis C virus (HCV) core antigen assay has recently been developed. We compared viral disappearance and first-phase kinetics between commercially available core antigen (Ag) assays, Lumipulse Ortho HCV Ag (Lumipulse-Ag), and a quantitative HCV RNA PCR assay, Cobas Amplicor HCV Monitor test, version 2 (Amplicor M), to estimate the predictive benefit of a sustained viral response (SVR) and non-SVR in 44 genotype 1b patients treated with interferon (IFN) and ribavirin. HCV core Ag negativity could predict SVR on day 1 (sensitivity = 100%, specificity = 85.0%, accuracy = 86.4%), whereas RNA negativity could predict SVR on day 7 (sensitivity = 100%, specificity = 87.2%, accuracy = 88.6%). None of the patients who had detectable serum core Ag or RNA on day 14 achieved SVR (specificity = 100%). The predictive accuracy on day 14 was higher by RNA negativity (93.2%) than that by core Ag negativity (75.0%). The combined predictive criterion of both viral load decline during the first 24 h and basal viral load was also predictive for SVR; the sensitivities of Lumipulse-Ag and Amplicor-M were 45.5 and 47.6%, respectively, and the specificity was 100%. Amplicor-M had better predictive accuracy than Lumipulse-Ag in 2-week disappearance tests because it had better sensitivity. On the other hand, estimates of kinetic parameters were similar regardless of the detection method. Although the correlations between Lumipulse-Ag and Amplicor-M were good both before and 24 h after IFN administration, HCV core Ag seemed to be relatively lower 24 h after IFN administration than before administration. Lumipulse-Ag seems to be useful for detecting the HCV concentration during IFN therapy; however, we still need to understand the characteristics of the assay.

Clinical usefulness of a new hepatitis C virus RNA extraction method using specific capture probe and magnetic particle in hemodialysis patients

Hemodialysis patients are a high-risk group for hepatitis C virus (HCV) infection. Assessment of HCV infection using HCV-RNA assay among dialysis patients is important for the issue of safety and environmental protection. However, polymerase chain reaction (PCR)-based methods are unsuitable for analyzing samples from dialysis patients because the conventional centrifugal extraction method fails to eliminate heparin, a potent inhibitor of PCR. In this study, we evaluated the usefulness of a HCV-RNA extraction method using probes and magnetic particles for hemodialysis patients in comparison with the centrifugal method. The study population consisted of 17 HCV antibody-positive patients undergoing hemodialysis. These 17 patients consisted of 12 HCV carrier patients and five patients with past HCV infection. One hundred and two samples from these patients were measured using the centrifugal and magnetic methods. Moreover, we prepared five standards that included theoretically 5 KIU/mL of HCV. One was made from non-HD patient's serum and the other four were from hemodialysis patients' serum. These standards were measured using the two methods. False-negative results were not observed with the magnetic method, but were observed in five out of 102 samples with the centrifugal method. Studies using standard samples revealed that accurate HCV-RNA measurement is achieved using the magnetic method. In conclusion, the present study showed that this magnetic extraction method is a highly reproducible and reliable assay to obtain correct information about the presence of the infective virus itself in the hemodialysis setting. Precise identification of HCV-RNA using this specific method is considered to be useful in preventing HCV infection in hemodialysis units.

Identification of a specific marker for hepatitis C virus infection using capillary zone electrophoresis

BACKGROUND

Hepatitis C virus (HCV) infection is now becoming a common health problem in both developed and developing countries. The limitation of the available diagnostic approaches enhances the efforts to have a rapid, sensitive, and specific diagnostic testing for HCV infection. Capillary zone electrophoresis (CZE) is a fully automated analytical technique whose popularity is quickly increasing in the clinical chemistry laboratory. CZE can analyze nanoliters or less of samples with detection sensitivity at the attomole level (10(-18) mol) or less.

METHODS

CZE was optimized for the identification of a specific marker of HCV infection. The performance characteristics of the CZE for the detection of HCV RNA peak were evaluated in comparison with standard nested PCR.

RESULTS

A characteristic peak at 2.72 min was identified only in the CZE electropherogram of urine samples from HCV-infected individuals. The nature of the characteristic peak was investigated and confirmed to be HCV RNA using PCR and other biochemical treatments including RNase, DNase, and trypsin enzymes. CZE showed high degrees of sensitivity (94%) and specificity (96%) in comparison with the nested PCR.

CONCLUSION

CZE provides a rapid, inexpensive, sensitive, and specific analytical method for diagnosis and mass screening of a large number of HCV-infected individuals.

Inter-laboratory comparison of qualitative and quantitative detection of hepatitis C (HCV) virus RNA in diagnostic virology: a multicentre study (MS) in Italy

BACKGROUND

The importance of the standardisation of nucleic acid amplification technology (NAT) assays for the detection of hepatitis C virus RNA is well known today, as many studies carried out in different European countries attest. The results of a previous study performed in Italy (J. Clin. Virol. 1 (2003) 83) by the Italian Society of Clinical Microbiology (AMCLI) showed that the use of external reference standards and of multicentre collaborative studies significantly improves laboratory performance for the qualitative evaluation of HCV RNA.

OBJECTIVES

the AMCLI organised a new study on the standardisation of both the qualitative and the quantitative evaluation of HCV RNA with NAT in order to improve the implementation of the diagnostic methods for HCV RNA detection.

STUDY DESIGN

seventeen diagnostic centres of major Italian Hospitals participated in this quality control study. The study consisted of testing three panels, each made up of 10 coded samples including negative and positive samples. Positive samples contained four levels of HCV RNA (genotype 1).

RESULTS AND CONCLUSION

Seven out of 510 qualitative results obtained were incorrect (1.4%), two false negative and five false positive. The results gave a sensitivity of 99.5% and a specificity of 95.8%. Regarding quantitative tests, the geometric mean (GM) and standard deviation (S.D.) could be calculated only for the three highest HCV RNA levels. The percentage of results within the range of GM +/- 0.5 log(10) varied from 91% to 100%. Some laboratories had some difficulty in the exact quantification of the lowest (3.00 log IU/ml) as well as of the highest viral levels (6.35 log IU/ml) values, very near to the limits of the dynamic range of the assays. The comparison of the results of this study with that previously carried out one confirms that a regular participation in external quality assessment (EQA) assures the achievement of a high proficiency level in the diagnosis of HCV infection.

Multicentre quality control study for detection of Mycobacterium tuberculosis in clinical samples by nucleic amplification methods

The aim of this study was to evaluate the laboratory performance of nucleic acid amplification tests (NATs) for detection of the Mycobacterium tuberculosis complex. A proficiency panel consisting of eight sputum specimens and four specimens diluted in phosphate-buffered saline (PBS) was sent to 82 laboratories in 23 countries by the Quality Control for Molecular Diagnostics (QCMD) TB programme. The performance of different NATs was analysed in combination with a questionnaire on the applied methods. Seventy-eight participants (95.2%) contributed a total of 85 evaluable data sets. The percentage of correct results on the eight sputum samples was 86.3% (586/679). Of the sputum specimens considered as 'smear-negatives' (650 CFU/250 micro L), only 61.2% (104/170) were reported positive. The percentage of correct results for the three scored PBS samples was 75.7% (193/255). The total number of false-positive results was 11 (4.3%); these were reported for seven (8.2%) of the 85 data sets. In 32 (37.6%) data sets an 'in-house' NAT method was used, and in 53 (62.4%) sets a commercial assay was tested. The percentage of data sets achieving correct results on all sputum samples was 35.3% and 37.8%, respectively. For the PBS samples this was 45.8% and 41.5%. Overall, the results of this study demonstrated that the performance of NATs for the detection of M. tuberculosis has improved since previous studies. The percentage of false-positives has decreased considerably. However, a large number of procedures still lack sufficient sensitivity for application to smear-negative samples.

Reliability of hepatitis C virus core antigen assay for detection of viremia in HCV genotypes 1, 2, 3, and 4 infected blood donors: a collaborative study between Japan, Egypt, and Uzbekistan

Nucleic acid amplification-based methods are used for confirmation of viremia in antibody to hepatitis C virus (anti-HCV)-positive patients. However, this technology is labor intensive, time consuming, requires complex laboratory conditions, and expensive. The aim of this study was to evaluate the sensitivity and specificity of the HCV core antigen (HCVcAg) assay as an alternative approach for confirmation of viremia in HCV-infected subjects with HCV genotype 1-4. Two hundred forty-six asymptomatic HCV RNA- positive donors were enrolled in this study, consisting of 122 blood donors from Egypt (116 with genotype 4, 4 with genotype 1, and 2 with 1 + 4 genotypes), 109 from Japan (85 with genotype 1, and 24 with genotype 2), and 15 from Uzbekistan (all with genotype 3). A total of 234 (95.1%) of 246 RNA-positive specimens were detected by the HCVcAg assay; the sensitivity of HCVcAg assay consisted 93.4, 100, 100, and 94.8% for genotypes 1, 2, 3, and 4, respectively in comparison with RT-PCR assay. The specificity of the assay was confirmed in the absence of the false-positive results among 53 anti-HCV-negative, but anti-Schistosoma mansoni (anti-Sm) positive donors from Egypt. A positive correlation between HCVcAg and HCV RNA concentration levels (r = 0.671, P < 0.05) was observed among specimens with HCV genotype 4. The mean HCVcAg level was significantly lower in specimens with genotype 4 (2,935 fmol/L) comparing to genotypes 1, 2, and 3 (5,034, 4,962, and 4,740 fmol/L, respectively). No specific mutation was found in the core-encoding region of the studied specimens. In conclusion, HCVcAg is shown to be specific, sensitive, and informative qualitative index for HCV viremia in asymptomatic carriers.

Évaluation du risque infectieux résiduel chez les donneurs de sang au Centre national de transfusion sanguine de Conakry

To estimate the risk of transmitting human immunodeficiency virus (HIV) and hepatitis B virus (HBV) by blood transfusion. Residual risks for each of infections have been calculated from incidence cases number, rate incidence for 100,000 person-years has been estimated and multiplied by the period of mute serological window for each agent (22 days for HIV and 56 for HBV) in order to estimate the residual risk. This study shows that risk residual is 1/121 blood donations for HBV and 1/8562 blood donations for HIV. The obtained results show that the HIV and HBV transmission risk due to blood transfusion according to the present practice at the NCBT of Conakry is important.

False-positive results and contamination in nucleic acid amplification assays: suggestions for a prevent and destroy strategy

Contamination of samples with DNA is still a major problem in microbiology laboratories, despite the wide acceptance of PCR and other amplification techniques for the detection of frequently low amounts of target DNA. This review focuses on the implications of contamination in the diagnosis and research of infectious diseases, possible sources of contaminants, strategies for prevention and destruction, and quality control. Contamination of samples in diagnostic PCR can have far-reaching consequences for patients, as illustrated by several examples in this review. Furthermore, it appears that the (sometimes very unexpected) sources of contaminants are diverse (including water, reagents, disposables, sample carry over, and amplicon), and contaminants can also be introduced by unrelated activities in neighboring laboratories. Therefore, lack of communication between researchers using the same laboratory space can be considered a risk factor. Only a very limited number of multicenter quality control studies have been published so far, but these showed false-positive rates of 9-57%. The overall conclusion is that although nucleic acid amplification assays are basically useful both in research and in the clinic, their accuracy depends on awareness of risk factors and the proper use of procedures for the prevention of nucleic acid contamination. The discussion of prevention and destruction strategies included in this review may serve as a guide to help improve laboratory practices and reduce the number of false-positive amplification results.

Molecular and diagnostic clinical virology in real time

During the last decade, the application of both qualitative and quantitative nucleic acid detection techniques has had a major impact on diagnostics in clinical virology. Both signal and target amplification-based systems are currently used routinely in most if not all virology laboratories. However, commercial assays are only available for a very limited number of targets, and this has resulted in the development and introduction of assays developed in-house for most viral targets. With improved and automated nucleic acid sample isolation techniques, as well as real-time detection methods, a new generation of assays for most clinically important viruses is being developed. These technological improvements also make it possible to generate results with a very short turnaround time. As an example of a more individual-patient disease-management concept, we have introduced in our clinical setting the quantitative detection of Epstein-Barr virus (EBV) in T-cell-depleted allogeneic stem cell transplant patients. This has enabled us to develop models for pre-emptive anti-B-cell immunotherapy for EBV reactivation, and for reducing not only the incidence of EBV lymphoproliferative disease (EBV-LPD), but the virus-related mortality. It is now also feasible to introduce molecular testing for those viruses that can easily be detected using classical virological methods, such as culture techniques or antigen detection. Prospective studies are needed to evaluate the clinical importance of the additional positive samples detected. It should, however, be clear that a complete exchange of technology is unlikely to occur, and that complementary methods should stay operational, making possible the discovery of new viruses. Furthermore, the ability to characterise viruses more easily by sequencing opens new possibilities for epidemiological studies. There is also an urgent need, with regard to molecular diagnostic methods, for the introduction and use of standardised materials and participation in international quality control programmes. Finally, with the introduction of a universal internal control throughout the whole procedure, the accuracy of the results generated is warranted.

Influence of maternal human immunodeficiency virus (HIV) co-infection on vertical transmission of hepatitis C virus (HCV): a meta-analysis

BACKGROUND

Maternal co-infection with human immunodeficiency virus (HIV) has been implicated as a potentially important co-factor for enhanced vertical transmission of hepatitis C virus (HCV). In previous reports, however, methodological issues (notably small sample sizes) have limited accurate evaluation of the contribution of maternal co-infection with HIV on the risk of vertical transmission of HCV.

METHODS

A systematic review and subsequent meta-analysis of current published and unpublished reports was performed. Odds ratios (OR) and 95% CI for individual studies were calculated with maternal HIV serostatus as the exposure measure and HCV vertical transmission as the outcome measure. Overall summary estimates were then calculated using a random effects model that estimates a weighted average of OR from individual studies.

RESULTS

In total, 2382 infants from 10 studies were included in an analysis of HCV-infected mothers (defined by anti-HCV+ antibody assays) with and without concomitant HIV infection. The risk estimate (OR) of HCV vertical transmission was 2.82 (95% CI: 1.78-4.45; P = 0.00001) from anti-HCV+/HIV+ co-infected mothers compared with anti-HCV+/HIV- mothers. In a subanalysis of 1327 infants born to viraemic (HCV RNA+) mothers, the risk estimate of HCV vertical transmission was 1.97 (95% CI: 1.04-3.74; P = 0.04) from HCV viraemic/HIV+ co-infected mothers compared with HCV viraemic/HIV- mothers.

CONCLUSIONS

Results from this meta-analysis of observational studies suggest that the risk of HCV vertical transmission is higher in infants born to HIV co-infected mothers.

Management of healthcare workers after occupational exposure to hepatitis C virus

The increasing rate of hepatitis C virus (HCV) infection in the community means that there is increased risk of occupational exposure for healthcare workers. In metropolitan hospitals in Victoria, we found that 80-150 healthcare workers have occupational exposures from HCV-infected patients annually. As there is a 1.8%-3% risk of transmission of HCV from a needlestick injury, two to five healthcare workers are likely to acquire HCV each year in Victoria. These needlestick injuries pose a personal, legal and professional risk to healthcare workers and their patients. Recent information shows that early antiviral treatment of acute HCV infection has high cure rates. Current local and international protocols for management of healthcare workers exposed to HCV do not address these issues. We propose a management protocol after needlestick injury that is stratified according to the likelihood of HCV acquisition and potential risk of staff-to-patient transmission, and that is consistent with the current legal and clinical context of HCV infection in Australia.

Reliability of nucleic acid amplification methods for detection of Chlamydia trachomatis in urine: results of the first international collaborative quality control study among 96 laboratories

The first European Quality Control Concerted Action study was organized to assess the ability of laboratories to detect Chlamydia trachomatis in a panel of urine samples by nucleic acid amplification tests (NATs). The panel consisted of lyophilized urine samples, including three negative, two strongly positive, and five weakly positive samples. Ninety-six laboratories in 22 countries participated with a total of 102 data sets. Of 204 strongly positive samples 199 (97.5%) were correctly reported, and of 506 weakly positive samples 466 (92.1%) were correctly reported. In 74 (72.5%) data sets correct results were reported on all samples, and 17 data sets (16.7%) showed either one false-negative or one false-positive result. In another 11 data sets, two or more incorrect results were reported, and two data sets reported a false-positive result on one negative sample. The Roche COBAS Amplicor test was performed in 44 (43%) data sets, the Abbott LCx assay was performed in 31 (30%) data sets, the Roche Amplicor manual assay was performed in 9 (9%) data sets, an in-house PCR was performed in 9 (9%) data sets, the Becton Dickinson ProbeTec ET assay was performed in 5 (4.9%) data sets, and the GenProbe TMA assay was performed in 4 (3.9%) data sets. The results of the Roche Amplicor manual (95.6% correct), COBAS Amplicor (97.0%), and Abbott LCx (94.8%) tests were comparable (P = 0.48). The results with the in-house PCR, BD ProbeTec ET, and GenProbe TMA tests were reported correctly in 88.6, 98, and 92.5% of the tests, respectively. Freeze-drying of clinical urine specimens proved to be a successful method for generating standardized, stable, and easy-to-transport samples for the detection of C. trachomatis by using NATs. Although the results, especially the specificity, for this proficiency panel were better than most quality control studies, sensitivity problems occurred frequently, underlining the need for good laboratory practice and reference reagents to monitor the performance of these assays.

Managing occupational risks for hepatitis C transmission in the health care setting

Hepatitis C virus (HCV) infection is a significant contemporary health problem in the United States and elsewhere. Because it is primarily transmitted via blood, hepatitis C infection presents risks for both nosocomial transmission to patients and occupational spread to health care workers. Recent insights into the pathogenesis, immunopathogenesis, natural history, and treatment of infection caused by this unique flavivirus provide a rationale for the use of new strategies for managing occupational hepatitis C infections when they occur. This article reviews this developing information. Recently published data demonstrate success rates in the treatment of "acute hepatitis C syndrome" that approach 100\%, and although these studies are not directly applicable to all occupational infections, they may provide important clues to optimal management strategies. In addition, the article delineates approaches to the prevention of occupational exposures and also addresses the difficult issue of managing HCV-infected health care providers. The article summarizes currently available data about the nosocomial epidemiology of HCV infection and the magnitude of risk and discusses several alternatives for managing exposure and infection. No evidence supports the use of immediate postexposure prophylaxis with immunoglobulin, immunomodulators, or antiviral agents. Based on the very limited data available, the watchful waiting and preemptive therapy strategies described in detail in this article represent reasonable interim approaches to the complex problem of managing occupational HCV infections, at least until more definitive data are obtained.

Multicentre Italian Study Group (MISG) for the standardisation of hepatitis C virus (HCV) PCR

BACKGROUND

Several studies on standardisation of NAT assays for diagnosis of hepatitis C virus (HCV) infection have been carried out in European countries. In fact the widespreading use of nucleic acid amplification technology (NAT) in diagnostic centres for the evaluation of the HCV infection, requires the application of reference external standards to control laboratory performance; but up to date they are not routinely used.

OBJECTIVES

Fifteen diagnostic centres of major Italian Hospitals participated to a quality control study for the standardisation of polymerase chain reaction (PCR)-based HCV-RNA detection, organised by the Committee for the Study of Biotechnology (CoSBio) of the Italian Society of Clinical Microbiology (AMCLI). All the participant centres (PC) used commercial assays, automated or semi-automated.

STUDY DESIGN

The study was performed in four rounds. Altogether each centre received 14 reference negative and 22 reference positive sera. The range of copies number per ml of the reference positive sera was 10(4)-10(7).

RESULTS AND CONCLUSIONS

Considering the 540 samples tested, 4.54% of false negative (FN) and 4.28% of false positive (FP) results were reported. Thereafter the sensitivity and the specificity were 95.65 and 95.89%, respectively. The errors were distributed among seven out of the 15 PCs. The percentage of FP results was uniformly distributed in each shipment, whereas FN results emerged with the sera at lower HCV genome copies number. The analysis of the data obtained suggests that FP as well as FN results may be attributable to errors or to others problems of laboratories. To improve the performance of Italian, as well as of laboratories throughout the world, the use of external reference standards in multicentre collaborative studies will be required.

Review article: indicators and predictors of response to anti-viral therapy in chronic hepatitis C

The complications of chronic hepatitis C, including cirrhosis and hepatocellular carcinoma, are expected to increase dramatically world-wide over the next 10-20 years. Immunomodulatory/anti-viral therapy, employing interferon alfa both alone and in combination with ribavirin, affords the only effective treatment for hepatitis C. Accurate early prediction of response to interferon therapy may decrease or eliminate unnecessary or ineffective treatment, permit greater flexibility in tailoring therapy on an individual basis, and enhance the cost-effectiveness of treatment. Liver biopsy provides valuable information about the baseline severity and subsequent progression of hepatitis C. Severe fibrosis or cirrhosis on the pre-treatment liver biopsy is associated with decreased response rates. The measurement of viral RNA levels and genotyping may be used to optimize individual patient treatment. Genotype non-1 and a low viral load are the most significant pre-treatment indicators of sustained virological response. The most reliable predictor of a poor virological response is continued seropositivity for viral RNA during therapy. Therefore, a decision to stop or continue treatment can be based on a positive viral RNA test at 12 weeks for interferon-naive patients receiving interferon or pegylated interferon therapy.

A novel antigen detection immunoassay for field diagnosis of hepatitis C virus infection

The limitations of dominant methods-based on the detection of anti-HCV antibodies or HCV viremia currently used for the diagnosis of HCV infection enhance efforts to have a rapid, simple, sensitive, and specific alternative diagnostic approach to detect viral antigens. A highly reactive IgG antibody was raised to HCV-NS4 recombinant antigen. The produced antibody showed no cross-reactivity with the other HCV structural and nonstructural recombinant antigens (C1 + 2, C3 + 4, E2/NS1, NS3, NS5). The well established ELISA technique was adapted to detect the new target HCV-NS4 antigen in serum samples. Extremely high agreement was found between the results of ELISA and qualitative detection of HCV-RNA, using a RT-PCR test as a gold standard for the diagnosis of HCV infection. Based on these encouraging results, a novel enzyme immunoassay; dot-ELISA was developed for rapid (approximately 5 min) and simple qualitative detection of the target HCV antigen in serum. The developed method detected the HCV target antigen in 95% of serum samples from HCV infected individuals, with a specificity of 97% using sera of noninfected individuals in comparison with PCR test. The antigen detection method showed high predictive values of positive (99%) and negative (90%). Moreover, the dot-ELISA could detect the HCV target antigen in sera negative for anti-HCV Abs, but positive for HCV-RNA, and in sera of HCV infected individuals with low viremia, as well as those with high viremia, using quantitative RT-PCR. Accordingly, the developed highly sensitive and specific HCV antigen detection method could be applied for mass screening of HCV infection.

Quality control in nucleic acid testing--where do we stand?

Quality control has been playing an increasingly important role in the implementation of nucleic acid amplification techniques (NATs) for clinical diagnosis since the introduction of these methods in the early 1990s. Initial multicenter studies involving hepatitis B virus (HBV), hepatitis C virus (HCV), Mycobacterium tuberculosis, and human immunodeficiency virus type 1 (HIV-1) revealed serious problems in specificity (false-positive rates of ca. 40%) and sensitivity, large variations in quantitative results, and a plethora of units (largely not comparable between assays). The problem areas identified included the need for standardized reagents and common units, contamination control mechanisms, inhibition control mechanisms, genotype-independent detection and quantitation, facilitated nucleic acid isolation procedures, clinically relevant dynamic ranges, and internal run controls. Progress made in each of these areas will be discussed. In addition to the above-mentioned problem areas, the value of external quality control of existing and evolving NATs was recognized. To this end, the European Union Quality Control Concerted Action for Nucleic Acid Amplification in Diagnostic Virology was established in May 1998. During its three-and-a-half years of existence, a total of 14 proficiency panels containing 8-13 well-characterized, simulated clinical samples of various viral loads and genotypes were prepared for herpesviruses (herpes simplex virus, human cytomegalovirus), blood-borne viruses (HBV, HCV, HIV-1), enteroviruses, and Chlamydia trachomatis, distributed to up to 20 different countries, and tested by up to 97 different laboratories. The results show dramatic improvement in specificity (false-positive rates <3% for most panels), presumably due to a generally greater expertise of participating laboratories, more frequent use of enzymatic or mechanical contamination control mechanisms, and increased utilization of standardized reagents (commercial kits). However, considerable problems with sensitivity remain (false-negative rates up to 50%), reflecting the high detection limits of some commercial viral load kits still on the market as well as inadequate standardization of quantitation controls between assay systems. In conclusion, although considerable progress has been made, quality control of NATs in clinical diagnosis remains an ongoing challenge.

Clinical virology in real time

The ability to detect nucleic acids has had and still has a major impact on diagnostics in clinical virology. Both quantitative and qualitative techniques, whether signal or target amplification based systems, are currently used routinely in most if not all virology laboratories. Technological improvements, from automated sample isolation to real time amplification technology, have given the ability to develop and introduce systems for most viruses of clinical interest, and to obtain clinical relevant information needed for optimal antiviral treatment options. Both polymerase chain reaction (PCR) and nucleic acid sequence-based amplification (NASBA) can currently be used together with real time detection to generate results in a short turn-around time and to determine whether variants relevant for antiviral resistance are present. These new technologies enable the introduction of an individual patient disease management concept. Within our clinical setting, we have introduced this e.g. for quantitative detection of Epstein-Barr Virus (EBV) in T-dell depleted allogeneic stem cell transplant patients. This enabled us to develop models for pre-emptive anti B-cell immunotherapy for EBV reactivation, thereby effectively reducing not the incidence of EBV-lymphoproliferative disease but the virus related mortality. Furthermore, additional clinically relevant viruses can now easily be detected simultaneously. It also becomes more feasible to introduce molecular testing for those viruses that can easily be detected using classical virological methods, like culture techniques or antigen detection. Prospective studies are needed to evaluate the clinical importance of the additional positive samples detected. It should however be made clear that a complete exchange of technologies is unlikely to occur, and that some complementary technologies should stay operational enabling the discovery of new viruses. The implementation of these molecular diagnostic technologies furthermore warrants the use and introduction of standardized materials as well as participation in international quality control programs. Finally, the use of an internal control throughout the whole procedure not only ensures the accuracy of the results generated, but also is necessary to enable precise quantification of these results and to determine detection thresholds more accurately. Since so many targets do have clinical implications, laboratories might prefer to use universal internal controls before the in-house developed assays should be introduced in clinical virology.

External quality assessment program for qualitative and quantitative detection of hepatitis C virus RNA in diagnostic virology

To assess the performance of laboratories in detecting and quantifying hepatitis C virus (HCV) RNA levels in HCV-infected patients, we distributed two proficiency panels for qualitative and quantitative HCV RNA testing. The panels were designed by the European Union Quality Control Concerted Action, prepared by Boston Biomedica Inc., and distributed in May 1999 (panel 1) and February 2000 (panel 2). Each panel consisted of two negative samples and six positive samples, with HCV RNA target levels from 200 to 500,000 copies/ml. Panel 1 had four samples with at least 50,000 copies/ml, and panel 2 had two samples with at least 50,000 copies/ml. Fifty-seven laboratories submitted 45 qualitative and 35 quantitative data sets on panel 1, and 81 laboratories submitted 75 qualitative and 48 quantitative data sets on panel 2. In both panels, about two-thirds of the qualitative data sets and >90% of the quantitative data sets were obtained with commercial assays. With each panel, two data sets gave one false-positive result, corresponding to false-positivity rates of 1.3% and 0.8% for panel 1 and panel 2, respectively. Samples containing at least 50,000 copies/ml were found positive in 97% and 99% of the cases with panel 1 and panel 2, respectively. In contrast, the positive samples containing < or =5,000 copies/ml were reported positive in only 71% and 77% of the cases with panel 1 and panel 2, respectively. Adequate or better scores on qualitative results (all results correct or only the low-positive samples missed) were obtained in 84% (panel 1) and 80% (panel 2) of the data sets. In the analysis of quantitative results, 60% (panel 1) and 73% (panel 2) of the data sets obtained an adequate or better score (> or =80% of the positive results within the range of the geometric mean +/- 0.5 log(10)). Our results indicate that considerable improvements in molecular detection and quantitation of HCV have been achieved, particularly through the use of commercial assays. However, the lowest detection levels of many assays are still too high, and further standardization is still needed. Finally, this study underlines the importance of proficiency panels for monitoring the quality of diagnostic laboratories.

Qualitative detection of hepatitis C virus RNA: comparison of analytical sensitivity, clinical performance, and workflow of the Cobas Amplicor HCV test version 2.0 and the HCV RNA transcription-mediated amplification qualitative assay

The qualitative Cobas Amplicor hepatitis C virus (HCV) version 2.0 assay (HCV PCR) and the Bayer Reference Testing Laboratory HCV RNA transcription-mediated amplification assay (HCV TMA) were compared for analytical sensitivity, clinical performance, and workflow. Limits of detection were determined by testing dilutions of the World Health Organization HCV standard in replicates of 15 at concentrations of from 1.0 to 70 IU/ml. The limit of detection of the HCV PCR assay was calculated to be 45 IU/ml on initial testing and 32 IU/ml after resolution of gray zone results. The calculated limit of detection for HCV TMA was 6 IU/ml. To compare clinical performance, 300 specimens, grouped as follows, were evaluated: 112 samples that were indeterminate in an anti-HCV enzyme immunoassay (EIA) and for which HCV RNA was not detected by HCV PCR; 79 samples that were EIA positive and for which HCV RNA was not detected by HCV PCR; and 105 samples that were both EIA and HCV PCR positive. For these groups, interassay concordance ranged from 96.2% to 100%. In addition, three HCV PCR gray zone specimens and one neonatal specimen were also evaluated. A 64-sample run (full run, 91 specimens) required 5 h for testing by HCV TMA, whereas almost 8 h were required to test a full run of 22 specimens by HCV PCR. HCV TMA demonstrated excellent concordance with HCV PCR when clinical samples were tested. However, HCV TMA was more sensitive than HCV PCR, required less time for test result completion, and had a greater throughput.

Evaluation of the VERSANT HCV RNA 3.0 assay for quantification of hepatitis C virus RNA in serum

We assessed the performance of a new assay (VERSANT HCV RNA 3.0 [bDNA 3.0] assay [Bayer Diagnostics]) to quantitate HCV RNA levels and compared the results of the bDNA 3.0 assay to results of the Quantiplex HCV RNA 2.0 (bDNA 2.0) assay. Samples used in this study included 211 serum specimens from hepatitis C virus (HCV)-infected persons from two sites (Bordeaux and Marseille, France) with different genotypes; 383 serum specimens from HCV antibody-negative, HCV RNA-negative persons; and serial dilutions of World Health Organization (WHO) HCV RNA standard at a titer of 100,000 IU/ml. The specificity of the bDNA 3.0 assay was 98.2%. A high correlation was observed between expected and observed values in all dilutions of WHO standard (r = 0.9982), in serial dilutions of pooled samples (r = 0.9996), and in diluted sera from different HCV genotypes (r = 0.9930 to 0.9995). The standard deviations (SD) for the within-run and between-run reproducibility of the bDNA 3.0 assay were <or=0.2 and <or=0.14, respectively. The intersite SD ranged from 0.03 to 0.14. The bDNA 3.0 assay results were positively correlated with the bDNA 2.0 assay results (r = 0.9533). Taking in account the overall performance, this assay could be used as a routine tool for the HCV RNA quantification.

Sensitivity of HCV RNA and HIV RNA blood screening assays

BACKGROUND

The FDA requirement for sensitivity of viral NAT methods used in blood screening is a 95-percent detection limit of 100 copies per mL, whereas the NAT screening system should have a sensitivity of at least 5000 copies per mL per individual donation. According to the Common Technical Specifications of the European Directive 98/79/EC for in vitro diagnostics, viral standard dilutions (calibrated against the WHO standard) should be tested at least 24 times for a statistically valid assessment of the 95-percent detection limit.

STUDY DESIGN AND METHODS

Viral standard dilution panels (PeliCheck, VQC-CLB) were prepared for HCV RNA genotypes 1 and 3 and for HIV RNA genotypes B and E. In a multicenter study, 23 laboratories tested the panels all together in 8 to 91 test runs per NAT method.

RESULTS

The following 95-percent detection limits (and 95% CIs) were found on the HCV RNA genotype 1 reference panels (shown as geq/mL): Gen-Probe TMA, 85 (64-118); AmpliScreen, 126 (83-225); AmpliScreen with NucliSens Extractor, 21 (13-44); Amplicor with NucliSens Extractor, 69 (50-102), and Amplicor with Qiagen extraction technology, 144 (74-102). On HIV RNA genotype B dilution panels, the following 95-percent detection limits were found (shown as geq/mL): Gen-Probe TMA, 31 (20-52); AmpliScreen, 126 (67-311); AmpliScreen with NucliSens Extractor, 37 (23-69), and NucliSens QL assay, 123 (51-566). HIV RNA genotype E panels were detected with equal sensitivity as HIV RNA genotype B panels. In the Gen-Probe TMA assay, the 50-percent detection limits on HIV RNA type B and type E were 3.6 (2.6-5.0) and 3.9 (2.4-5.8) geq per mL, respectively. The HCV RNA genotype 1 and 3 standards were detected with equal sensitivity.

CONCLUSION

The differences in sensitivity between NAT assays can be explained by the input of isolated viral nucleic acid in the amplification reactions. The FDA requirements for sensitivity of NAT blood screening assays can be met by the Gen-probe TMA, as well as by the AmpliScreen assays, particularly when combined with the NucliSens Extractor.

High prevalence of HCV infection among the general population in a rural area of central Italy

The hepatitis C virus infection (HCV) is the most frequent cause of hepatic infection in Europe. In Italy, anti-HCV positivity values are extremely variable, depending on the age and geographic location of the population being analysed. The aims of the study were: (1) evaluating positivity for anti-HCV antibodies in various age groups and determining the HBsAg in a mountainous and predominantly farming area in central Italy; (2) assessing some anamnestic and clinical variables through a questionnaire, submitted during the taking of blood samples, in order to determine HCV exposure and risk factors for the target population. 344 subjects selected by random sampling among 3308 people, older than 16, were considered as the target population. A prevalence study was carried out. The sources of data were: blood samples taken to carry out the HCV positivity test; a questionnaire including items about exposures at risk and case-historical and clinical patient data. The risk of infection was evaluated by a multiple logistic regression model. The inferred HCV+ prevalence rate is 22.4/100 (95% confidence interval (CI): 20.8-24.1). An increasing age trend is shown with a higher positive predominance among females (28.99/100 vs. 14.29/100 in males). The positive HBsAg prevalence in the examined survey is 1.2/100. Variables associated with the HCV occurrence are case history of pneumonopathy (OR: 4.9) and exposure to parenteral therapies with glass syringes (OR: 3.3). This study is consistent with literature about the hypothesis of a north-south geographic gradient in the hepatitis C occurrence in Italy. Data clearly show the effects of the inappropriate use of medical or surgery practices on the population, with particular reference to the use of glass syringes. No elements prove that the farming features of the area may be predictive of HCV infection risk. The extent of the recorded prevalence values calls for the implementation of programmes aimed at detecting clusters or population areas at risk.

European proficiency testing program for molecular detection and quantitation of hepatitis B virus DNA

External quality control of hepatitis B virus (HBV) DNA detection remains an important issue. This study reports and compares the results obtained from two different proficiency panels for both the qualitative and quantitative assessment of HBV DNA. The panels were designed by the European Union Quality Control Concerted Action, prepared by Boston Biomedica, Inc., and distributed in May 1999 (panel 1) and February 2000 (panel 2). Each contained two negative samples and six positive samples with 10(3) to 10(7) copies/ml (panel 1) or 10(3) to 2 x 10(6) copies of HBV DNA per ml (panel 2). For panel 1, 42 laboratories submitted 20 qualitative (all in-house PCRs) and 37 quantitative (87% commercial assays) data sets. For panel 2, 51 laboratories submitted 25 qualitative (all in-house PCRs) and 47 quantitative (94% commercial assays) data sets. Five data sets (8.8%) in panel 1 and two data sets (2.8%) in panel 2 contained totals of six and two false-positives, respectively, corresponding to false-positive result rates of 5.3% for panel 1 and 1.4% for panel 2. The false-negative result rates of 10.5% for panel 1 and 17.4% for panel 2 were dependent on the detection levels of the assays employed as well as panel composition. In the qualitative analysis of all data sets, 47.4% (panel 1) and 51.4% (panel 2) had all samples correct. An adequate or better score (all correct or only the weak-positive sample missed) was obtained with 77.2% of the panel 1 samples and 68.1% of the panel 2 samples. In the quantitative analysis, 57.1% (panel 1) and 42.6% (panel 2) of the data sets achieved an adequate or better score (positive results within the acceptable range of the geometric mean +/- 0.5 log(10) of all positive results). These results demonstrate that while the qualitative performance of HBV detection has considerably improved compared to that of a previously published HBV proficiency study, the detection levels of many commercial quantitative assays are still too high to allow adequate quantitation of all relevant clinical samples.

Quantitation of viral load using real-time amplification techniques

Real-time PCR amplification techniques are currently used to determine the viral load in clinical samples for an increasing number of targets. Real-time PCR reduces the time necessary to generate results after amplification. In-house developed PCR and nucleic acid sequence-based amplification (NASBA)-based systems combined with several detection strategies are being employed in a clinical diagnostic setting. The importance of these assays in disease management is still in an exploration phase. Although these technologies have the implicit capability of accurately measuring DNA and RNA in clinical samples, issues related to standardization and quality control must be resolved to enable routine implementation of these technologies in molecular diagnostics.

The natural history of hepatitis C virus infection

The natural history of HCV infection remains ill-defined. The knowledge accumulated on the progression of HCV to date is important, however. It is now abundantly clear that the progression of disease is generally slow, and the development of cirrhosis and its complications is a possibility, not a probability as hitherto thought. Predicting the outcome remains a quandary for clinicians. Ultimately it will be possible to define the natural history of hepatitis C infection through a combination of research in the fields of virology, immunology, and molecular biology and by monitoring the biochemical and histologic progress of the disease. Only then will it be possible to intervene appropriately and develop new therapies to prevent the progression to cirrhosis and hepatocellular carcinoma.

Management of interferon therapy nonresponders

Despite improvements in the therapies for chronic hepatitis C virus (HCV) over the past several years, many patients still fail to become hepatitis C virus ribonucleic acid (HCV-RNA) undetectable during treatment and are classified as nonresponders. Providing treatment recommendations for these patients requires that the likelihood of achieving any benefit from another course of therapy be balanced with the natural history of chronic HCV. The management of nonresponders represents the most challenging of all aspects in the care of patients with chronic HCV. Retreatment of interferon non-responders with interferon and ribavirin has yielded a long-term virologic benefit in only 10% to 25% of patients. The efficacy of peginterferon and peginterferon with ribavirin for nonresponders has yet to be defined.

Hepatitis C virus testing of plasma pools by nucleic acid amplification technology: external quality assessment

BACKGROUND AND OBJECTIVES

Since 1 July 1999, in accordance with European regulations, only batches of blood products obtained from plasma pools tested and found to be non-reactive for hepatitis C virus (HCV) RNA are being released. As monitoring the performance of manufacturers involved in plasma pool testing is important to ensure reliable amplification techniques, the Istituto Superiore di Sanità, as the Italian regulatory authority, organized an external quality assessment study.

MATERIALS AND METHODS

A reference HCV RNA panel calibrated in international units (IU) was sent to each participant to be tested according to the validated procedure they routinely used in plasma pool testing. The panel consisted of 20 coded samples, four of which were obtained from a negative plasma pool. The remaining 16 samples, prepared by diluting the national reference preparation (ISS HCV RNA 0498), represented four half-log dilution series, each consisting of four samples containing 100, 32, 10 and 3.2 IU/ml of HCV RNA.

RESULTS

The overall performance of the laboratories was very satisfactory. All laboratories correctly identified the negative samples. The 100- and 32-IU/ml samples were both detected in 98.4% of the assays, while the 10- and 3.2-IU/ml samples were detected in 73.4 and 50.0% of the assays, respectively. No substantial differences were observed between in-house procedures and commercial kits.

CONCLUSION

This external quality assessment study showed that manufacturers of blood products have reached a high level of proficiency that fully complies with the European Pharmacopoeia requirements. This finding is reassuring in the context of the safety of blood products.

Screening standards in assisted reproductive technologies. Is the British Andrology Society recommendation to recruit cytomegalovirus negative semen donors only, a reasonable one?

The British Andrology Society recently recommended the exclusion of all cytomegalovirus (CMV) seropositive semen donors to prevent the risk of congenital CMV infection. The recommendation is based on the results of recent studies that identified a high percentage of symptomatic congenital CMV infections in newborns of women with CMV seropositivity pre-existing to pregnancy and on the fact that CMV can be detected in semen of CMV seropositive men. These are not new data. CMV seropositive women can infect their fetuses with their own latent CMV strain that can reactivate, or with an exogenous strain that can be transmitted to them by a sexual partner, but also by contacts, for example with an excreting child. The efficiency of these various ways of transmission to the fetus and the factors that could influence this transmission are for the moment completely unknown. An infectious virus is recovered by culture in the semen of <5% of CMV seropositive men. Exclusion of a large population of donors on the sole criteria of a positive CMV serology introduces the general message that this part of the male population is also not suitable as possible partners in couples who have no fertility problems. The problem of congenital infection in neonates of CMV seropositive women is a complex one that has just begun to be investigated. No data exists concerning this risk in the setting of assisted reproduction. We think that alternatives to the drastic BAS recommendation exist and should be more deeply discussed.

Detection of Helicobacter pylori virulence-associated genes

Helicobacter pylori is an important human pathogen and persistent colonization of the human gastric mucosa can cause severe gastrointestinal diseases. The bacterium should not be considered as a uniform organism, but as a population of closely related and yet genetically diverse bacteria. Several genes of H. pylori (such as vacA and cagA) have been identified as being virulence-associated and may have important clinical and epidemiological implications. Assessment of virulence-associated genes of H. pylori should be included in clinical and epidemiological studies as well as therapeutic trials, in order to stratify between patient groups, harboring H. pylori strains with particular virulence genotypes. Molecular determination of antibiotic resistance will be especially useful for treatment studies. Together with our increasing knowledge about the human genome, typing of H. pylori will facilitate the management of gastroenterological pathologies.

Quantitation of HCV RNA using real-time PCR and fluorimetry

Real-time PCR technology may provide an accurate and sensitive method to quantify hepatitis C virus (HCV) RNA. So far, studies have been carried out using the Taqman technology with the ABI Prism 7700 sequence detector. An alternative and simple real-time PCR assay is described with no probe requirement, based on the SYBR Green I dye and LightCycler fluorimeter. Amplicon synthesis was monitored continuously by SYBR Green I dye binding to double stranded DNA during PCR of the 5' HCV non-coding (NC) region. Specificity was verified by amplicon melting temperatures. An external standard curve was constructed with serial 10 fold dilutions of a modified synthetic HCV 5' NC RNA. A wide range linear relationship (up to 3.7x10(9) copies/ml) was observed between number of PCR cycle needed to detect a fluorescent signal and number of RNA copy. Intra- and inter-assay coefficients of variation were 0.7 to 2.1 and 3.7% respectively, indicating good reproducibility of the method. Thirty-three HCV positive sera of different genotypes were quantified by this method and gave similar but more sensitive results compared to the branched DNA (bDNA) technology.

Reliability of PCR-based detection of occult tumour cells: lessons from real-time RT-PCR

For the molecular detection of rare tumour cells in clinical samples, real-time reverse transcription-polymerase chain reaction (RT-PCR) offers two important advantages over conventional RT-PCR assays: the results are quantitative and, perhaps more importantly, it facilitates exact sensitivity controls on a per sample basis as well as exact comparison of different assay protocols. We report here on quantitative results obtained with different protocols for RNA isolation and cDNA synthesis for amplification of beta2-microglobulin transcripts using the light cycler system. Furthermore, housekeeping gene-specific PCRs were compared with PCRs specific for an artificial transcript (internal standard) detected simultaneously at a level comparable to the wild-type sequence. Artificial tyrosinase transcripts derived from a vector construct stably transfected into a human lymphoma cell line were used as a model to test the usefulness of artificial internal standards as an alternative to housekeeping genes. The highest RNA yields were obtained using a combination of phenol-chloroform extraction and the High Pure RNA Isolation Kit. Analysing beta2-microglobulin transcript-specific RT-PCRs, the highest sensitivity was obtained for cDNAs generated with Omniscript reverse transcriptase and oligo-p(dT)15 primer. Regarding patient blood samples, RT-PCRs specific for beta2-microglobulin, porphobilinogen deaminase and artificial tyrosinase transcripts provided quantitative data for all, for 18 out of 21, and for 10 out of 21 samples, respectively. Quantification of beta2-microglobulin transcripts by the light cycler system defined the protocol revealing the highest cDNA quality. Comparisons of quantitative data from RT-PCRs specific for beta2-microglobulin, porphobilinogen deaminase and artificial tyrosinase transcripts enabled us to determine a close range for crossing points within which sufficient cDNA quality can be guaranteed, even for the detection of rare transcripts. PCRs specific for the artificial internal standard are ideally suited for cDNA quality assessment on a per sample basis.