Longitudinally profiling neutralizing antibody response to SARS coronavirus with pseudotypes

The severe acute respiratory syndrome-associated coronavirus (SARS-CoV) spike protein (S) is a major target for neutralizing antibodies. Retroviral SARS-CoV S pseudotypes have been constructed and used to develop an in vitro microneutralization assay that is both sensitive and specific for SARS-CoV neutralizing antibodies. Neutralization titers measured by this assay are highly correlated to those measured by an assay using replication-competent SARS-CoV. No cross-neutralization occurred with human sera known to contain antibodies to coronavirus strains OC43 and 229E. The pseudotype assay was used to profile neutralizing antibody responses against SARS-CoV S in sequential serum samples taken from 41 confirmed SARS patients during the 2003 outbreak in Hong Kong and shows long-lasting immunity in most recovered patients. The pseudotype assay does not require handling live SARS virus; it is a useful tool to determine neutralizing titers during natural infection and the preclinical evaluation of candidate vaccines.

Development of a novel human immunodeficiency virus type 1 subtyping tool, Subtype Analyzer (STAR): analysis of subtype distribution in London

We have developed a high throughput computational tool for assigning subtype to HIV-1, based solely on protease and reverse transcriptase (PR-RT) amino acid sequence, generated routinely for clinical assessment of genotypic drug resistance. Subtype-specific profiles were created by generation of position-specific scoring matrices (PSSMs) from multiple amino acids alignments of HIV-1 sequence data from GenBank, phylogenetically divided into subtypes A, AG, B, C, D, F/K, G, H, and J and the separate groups N and O. Query sequences of unknown subtype are aligned with these profiles and a score is derived by comparing each amino acid position in the unknown sequence to the normalized frequency distribution of amino acids at the corresponding positions in the subtype alignments. The highest score is used to assign subtype to the query sequence. Leave one out cross-validation analysis showed the Subtype Analyzer (STAR) was 99% accurate in subtype assignation. STAR can be updated with additional subtype-specific sequence data from sequence databases. STAR was used to classify HIV-1 PR-RT sequences from 843 HIV-1 clinical isolates submitted for drug resistance profiling in London. Within this dataset 26.9% of sequences were classified by STAR as non-B subtypes.

Characterization of HIV type 1 clades in the Caribbean using pol gene sequences

To date, 11 HIV-1 M group clades, A to K, have been characterized, displaying different distributions, prevalences, and biological properties. Approximately 90% of new HIV-1 infections occur in developing countries, including the Caribbean. However, information on HIV-1 subtypes from this region is limited. We report subtype characterization of viruses from 71 individuals, obtained during the period 2000-2002. RNA from the pol region was sequenced, generating data on subtype and drug resistance associated mutations for 71 specimens from 9 countries. Sixty-seven (94.4%) sequences were classified as clade B, three (4.2%) as D/B, and one (1.4%) as clade C. Numerous polymorphisms were observed, including some associated with drug resistance, but not signifying exposure to chemotherapy. This study adds to our knowledge of HIV-1 clades in the Caribbean, and indicates possibilities for monitoring HIV-1 chemotherapy.

HBV DNA levels and transmission of hepatitis B by health care workers

BACKGROUND

Laboratory-based study funded by the Research and Development Division of the Department of Health to inform the decision making on guidelines for the conduct of exposure prone procedures (EPPs) by health care workers who are hepatitis B carriers.

OBJECTIVES

Define the quantity and nature of hepatitis B virus (HBV) DNA in hepatitis carriers whose serum does not contain hepatitis B e antigen (HBeAg) and in surgeons previously cleared to conduct EPPs who have transmitted HBV to their patients.

STUDY DESIGN

Cross-sectional survey using HBV DNA quantification, genotyping and sequencing comparing transmitting surgeons and asymptomatic carriers.

RESULTS

HBV DNA could be detected and quantified in 64.5% (136 of 211) of carriers whose serum did not contain HBeAg with a median level 3.6 log(10) copies/ml (range of 5.7 log(10) copies). Pre-core mutation appeared not to affect the HBV DNA level, however, all surgeons carried codon 28 variants and transmitted these variants to their patients. The lowest HBV DNA level in a transmitting surgeon was 4 x 10(4) copies/ml.

CONCLUSIONS

Pre-core mutations are common in carriers whose serum does not contain HBeAg and do not specifically identify carriers whose HBV DNA levels are high. It was possible to define a level of virus above which transmission of hepatitis B during conduct of EPPs could not be excluded.

A 'first loop' linear epitope accessible on native hepatitis B surface antigen that persists in the face of 'second loop' immune escape

Murine monoclonal antibodies (mAbs) were raised following immunization with native mutant hepatitis B surface antigen (HBsAg) purified from human sera. A set of antibodies binding to a linear epitope carried between residues 121 and 129 of the s region was demonstrated. These antibodies were shown by cross-competition assays to bind to a single epitope whose antigenicity was influenced by the TTP motif lying between residues 125 and 127. This first loop epitope remained accessible on the surface of HBsAg in spite of major second loop mutations abrogating the normal a conformational epitopes. The mAb and its binding region in the first loop are important diagnostically and may represent an importance immunological target, one that is stable in the face of immunologically driven escape.

Development and clinical application of a fully controlled quantitative PCR assay for cell-free cytomegalovirus in human plasma

BACKGROUND

Cytomegalovirus (HCMV) disease continues to be a major problem in certain patient groups, including bone marrow transplant (BMT) recipients. The quantification of HCMV genome is clinically useful for the diagnosis of HCMV disease, for the virological surveillance of high-risk patients and for monitoring antiviral therapy.

OBJECTIVES

To develop a novel, robust, and fully controlled PCR (qPCR) for the quantification of HCMV DNA in plasma samples and to demonstrate its clinical usefulness in the BMT setting.

STUDY DESIGN

The newly developed HCMV qPCR employs cell culture-derived murine CMV as an internal control for both extraction and amplification. Following amplification using common primers, detection of both internal control and patient HCMV amplicons is by specific probes and a chemiluminescence microtitre plate system. Its performance was evaluated using the routine non-quantitative nested HCMV PCR on whole blood (NQPCR) and correlated with clinical events such as disease and antiviral therapy.

RESULTS

A high level of concordance (85.1%) was found between the novel assay and the NQPCR, with the qPCR being slightly more sensitive. The samples giving discordant results generally had levels of HCMV DNA close to the limit of detectability or had been stored for prolonged periods.

CONCLUSIONS

The use of plasma as an analyte by the newly developed assay avoids the detection of cell-associated virus. On the other hand, testing a comparatively large volume of plasma ensures that sensitivity is not compromised by not detecting cell-associated HCMV. In a small preliminary evaluation in BMT recipients, changes in HCMV 'viral load' correlated with initiation and discontinuation of antiviral therapy and were biologically plausible.

The prospective evaluation of a nested polymerase chain reaction assay for the early detection of Aspergillus infection in patients with leukaemia or undergoing allograft treatment

Patients with acute leukaemia or undergoing allogenic bone marrow transplantation at University College London Hospital Trust were screened for the presence of aspergillosis by polymerase chain reaction (PCR). Aspergillus DNA, from whole blood samples, was amplified by nested PCR to detect a 135 bp fragment in the mitochondrial region of Aspergillus fumigatus or A. flavus (121 bp). One colony-forming unit (CFU) per 2 ml of blood or 1-10 fg DNA could be detected. Patients at risk of aspergillosis were classified as probable or possible based on the European Organization for Research and Treatment of Cancer definitions. Antifungal drugs given were recorded. In four of 17 patients studied, infection was not suspected and the PCR was negative. Four patients were considered to have possible aspergillosis infection and were PCR positive on at least one occasion. Of the three patients in the probable group, four of the nine samples tested PCR positive from one patient and in another patient only one of nine samples tested positive. The remaining six patients were not suspected of having fungal infection but each had one or two PCR-positive results. In summary, six of seven patients thought to have clinical evidence of infection were PCR positive on at least one occasion and treatment with antifungals may have reduced infection below detectable levels.

Evidence for a dynamic host-parasite relationship in e-negative hepatitis B carriers

Anti-hepatitis Be (HBe) carriers are perceived as having low infectivity, with hepatitis B virus (HBV) DNA levels far below those seen in the HBeAg carrier. However, the temporal stability of HBV DNA in anti-HBe carriers remains poorly characterised. UK Department of Health guidelines use HBV DNA levels to define whether HBV-infected health care workers may perform exposure-prone procedures. Two samples separated by 1-23 years available from 147 carriers were analysed for precore variants and HBV DNA levels. Among 15 HBeAg carriers, HBV DNA was maintained at high levels. There was a 5 log(10) fold reduction in DNA in 11 individuals who developed anti-HBe during follow-up evaluation. Proportional changes in HBV DNA levels in anti-HBe carriers were similar to those in HBeAg carriers, although there was a trend for changes in viral DNA to be more marked in anti-HBe carriers followed up for longer periods. Closer sampling in 20 anti-HBe carriers demonstrated large fluctuations of DNA levels over short periods. Serum transaminases and precore mutant status at the outset failed to predict those in whom HBV DNA levels fluctuated. HBV DNA was below the detection threshold (<400 copies/ml) in 36 anti-HBe carriers at first sampling and remained so in all but 5 of these carriers. Twelve individuals who were previously viraemic lost detectable HBV DNA during follow-up evaluation. While HBV DNA levels are found to fluctuate in carriers, our results indicate that once below the threshold of detectability, levels are unlikely to rise. This is an important factor when assessing health care workers for exposure-prone procedures.

A genetic analysis of hepatitis C virus transmission between injection drug users

Hepatitis C virus (HCV) genotype 1a and 3a partial NS5B gene segment sequences obtained from 154 HCV-infected injection drug users were studied to determine the extent to which HCV transmission occurs between injection drug user communities in London, Edinburgh, Glasgow (United Kingdom), Marseilles (France), and Melbourne. Phylogenetic relationships between sequences were analyzed by conventional methods and by a recently developed method that numerically scores the extent of sequence segregation between groups through calculation of association indices. The association indices revealed that none of the cities sampled support an HCV population that is completely isolated from that circulating in the other cities. Sequences from Melbourne were most isolated, whereas those from London were most dispersed. This suggests that HCV transmission between these cities occurs, with London playing a pivotal role. The degree of city-specific segregation of HCV subtype 1a sequences was linearly related to that of subtype 3a, indicating that these subtypes have spread through similar transmission networks.

Quantification of HCV RNA levels and detection of core antigen in donations before seroconversion

BACKGROUND

Detection of HCV during the window phase of infection before seroconversion is important in blood screening. HCV RNA levels were measured before seroconversion and compared with HCV core antigen and anti-HCV detection.

STUDY DESIGN AND METHODS

A total of 41 plasma samples from 17 US plasmapheresis donors and one English National Blood Service donor in the window phase before seroconversion of HCV infection were tested for the presence of anti-HCV, HCV RNA, and HCV core antigen.

RESULTS

HCV RNA levels between 5.4 x 10(2) and 3.4 x 10(7) IU per mL were measured. HCV core antigen was detected in 11 of 18 donors at the same time point as RNA was detected.

CONCLUSIONS

A wide range of HCV RNA levels can be detected during the seronegative window phase of HCV infection. HCV core antigen can be used to detect HCV infection during the window phase of infection.

Automated screening of blood donations for hepatitis C virus RNA using the Qiagen BioRobot 9604 and the Roche COBAS HCV Amplicor assay

BACKGROUND AND OBJECTIVES

In order to reduce the potential for transmission of hepatitis C virus (HCV) from an RNA-positive, anti-HCV-negative blood donation, the National Blood Service (NBS) introduced nucleic acid amplification technology (NAT) testing for HCV in England and Wales. The objective of this study was to develop an automated assay using commercial components for the detection of HCV RNA in blood donations for transfusion.

MATERIALS AND METHODS

The Qiagen QIAamp 96 'Viral RNA' and 'Virus' BioRobot kits for HCV RNA extraction, and the Roche COBAS HCV Amplicor v2.0 and AmpliScreen v2.0 assays for polymerase chain reaction (PCR) amplification and detection, were investigated.

RESULTS

QIAamp technology and the BioRobot 9604 allow automation of the viral RNA extraction process. By combining the automated silica-membrane based QIAamp 96 Virus extraction and automated reverse transcription-polymerase chain reaction (RT-PCR) set-up with COBAS HCV AmpliScreen v2.0 amplification and detection it is possible to achieve a 95% detection level for HCV of 12.8 IU/ml. Cross-contamination studies have shown that use of the BioRobot 9604 does not pose a detectable contamination risk. Between 1999 and 2001, approximately 6.8 x 106 donations were tested in England and Wales, of which only four were found to contain RNA without anti-HCV.

CONCLUSIONS

This combination of methods results in an assay with a high sample throughput, little 'hands-on' time and fast turnaround time that is also sufficiently sensitive to allow testing of pools of up to 96 samples at a time. These methods have been successfully introduced into routine use within the NBS for release of blood components with a shelf-life of longer than 24 h.

Development and evaluation of an internally controlled semiautomated PCR assay for quantification of cell-free cytomegalovirus

Quantification of circulating human cytomegalovirus (HCMV) is useful in clinical contexts such as virological surveillance of bone marrow transplant recipients and monitoring of antiviral therapy. This report describes an internally controlled, quantitative, semiautomated, HCMV genome assay that was developed primarily to measure HCMV DNA in the plasma of severely leucopaenic patients. It exhibits greater sensitivity, wider dynamic range and higher sample throughput than a number of previously described commercial and "in-house" assays. Viral DNA extraction from EDTA plasma samples was automated using a BioRobot 9604 (Qiagen). HCMV strain AD169 was used to prepare a calibration curve and murine cytomegalovirus (MCMV) strain Smith was added as internal control to all calibration standards and test samples. Amplification was performed using a set of primers based on the HCMV UL50 region, capable of amplifying both human and murine CMV. The yield of biotinylated polymerase chain reaction (PCR) products was estimated using HCMV-specific and MCMV-specific enzyme-labelled probes and automated chemiluminescence detection. Log-transformed HCMV-to-MCMV signal ratios were calculated and used for quantification of test samples against simultaneously extracted MCMV-spiked calibration standards. Evaluation of the assay sensitivity by Probit analysis demonstrated a 95% probability of detection at 100 HCMV genomes per ml of plasma; the dynamic range was shown to be > or = 4 log(10). A total of 315 samples from 61 bone marrow transplant patients were analysed by both the quantitative PCR (qPCR) and by a previously validated nested nonquantitative PCR (NQPCR). A high level of concordance (90%) was observed between the two assays, although the qPCR assay exhibited slightly greater sensitivity.

Comparison of commercial assays for the quantification of HBV DNA load in health care workers: calibration differences

Until recently, carriers of hepatitis B virus (HBV) were allowed to undertake exposure prone procedures providing their serum did not contain HBeAg. However, the recent description of hepatitis B transmission events occurring from HBV-infected health care workers who conduct exposure prone procedures demonstrated that the then current Department of Health guidelines needed to be revised. As part of a series of studies carried out to determine if viral load measurements are a more secure means of assessing the conduct of exposure prone procedures, the suitability of commercially available assays for HBV DNA detection and quantification were investigated. This study describes a comparative analysis on the performances of three assays each based on a different methodology. The assays included the QUANTIPLEX HBV DNA Assay (bDNA), (Chiron Diagnostics Ltd.), the AMPLICOR HBV Monitor Test, (Roche Diagnostics Systems) and the Digene Hybrid Capture System HBV DNA Assay (Digene Corporation). Calibration curves from experiments using the Eurohep ad and ay HBV DNA standard controls indicated a close correlation between the three assays over the dynamic ranges claimed by the manufacturers, although the Quantiplex assay did appear to be over-reporting. This became more apparent when testing patients undergoing anti-viral therapy where the Quantiplex assay consistently over-reported by 0.5 log(10) when compared with the Amplicor assay. The results of this study indicate that based on its dynamic range, the Amplicor HBV Monitor test is the most appropriate assay for the routine investigation of anti-HBe carriers, which will have lower levels of HBV DNA. The investigation also highlights the need for using accepted standard HBV DNA control sera. This will be essential when using an assay to establish whether health care workers who are hepatitis B carriers can be allowed to perform exposure prone procedures under the new guidelines of the UK Department of Health.

Human T-cell leukaemia/lymphoma virus risk may be enhanced in some selected donor populations

BACKGROUND AND OBJECTIVES

Certain patient ethnic groups may require blood components from donors under-represented in the UK donor population. Selective recruitment of Afro-Caribbean donors is therefore necessary but was considered to pose an increased risk of human T-cell leukaemia/lymphoma virus (HTLV) infection. To assess this a seroprevalence study of HTLV was undertaken in Afro-Caribbean and Caucasian donors.

MATERIALS AND METHODS

Sera from 1100 Afro-Caribbean and 1100 Caucasian donors were tested for antibody to HTLV. Reactive samples were confirmed for specificity using an algorithm comprising two additional assays and polymerase chain reaction (PCR) where possible.

RESULTS

Six Afro-Caribbean donors (0.55%) were considered to be infected with HTLV I.

CONCLUSION

Donor selection in this case caused a significantly elevated prevalence of HTLV infection and serves as a warning of the need for care in the design of policies for selective donor recruitment.

Novel immunoassay for the detection of hepatitis B surface 'escape' mutants and its application in liver transplant recipients

Hepatitis B virus (HBV) strains with mutations in the surface gene are responsible for the failure of prophylaxis with hepatitis B immunoglobulin (HBIG) in a proportion of patients transplanted for HBsAg positive cirrhosis. So far, the emergence and evolution of these 'surface antibody escape' mutants have been studied by DNA sequencing. In this study the use of an immunoassay is described for diagnosis and characterisation of HBV recurrence after liver transplantation (OLT), based on a monoclonal antibody able to recognise both wild-type and mutant HBsAg. Pre- and post-transplant samples from 22 patients transplanted for HBsAg positive cirrhosis were studied: Group A: 12 patients who reinfected the graft despite receiving HBIG; Group B: 6 patients with no HBV recurrence with continuous HBIG; Group C: 4 patients with HBV recurrence without prophylaxis. By running the new assay in parallel with an immunoassay that is susceptible to HBsAg mutants, 4 of 12 cases were identified in Group A with HBV recurrence due to surface antibody escape mutants, whereas in 8 patients this was due to the wild-type HBV. The results from the immunoassays were confirmed in all cases by HBV DNA sequencing. The surface gene mutations in the 4 patients affected codons 144 and 145 and in one of these 4 patients HBV strains with mutations in both codons were detected before and after transplantation. The epitope recognised by the new monoclonal antibody that reacts with both wild-type and mutant HBsAg seems to remain stable in the HBIG-induced HBV mutants. This serological approach allows rapid and cost-effective screening for HBsAg escape mutants in the liver transplant setting and may be helpful in the selection of appropriate prophylaxis.

Novel immunoassay for the detection of hepatitis B surface 'escape' mutants and its application in liver transplant recipients

Hepatitis B virus (HBV) strains with mutations in the surface gene are responsible for the failure of prophylaxis with hepatitis B immunoglobulin (HBIG) in a proportion of patients transplanted for HBsAg positive cirrhosis. So far, the emergence and evolution of these 'surface antibody escape' mutants have been studied by DNA sequencing. In this study the use of an immunoassay is described for diagnosis and characterisation of HBV recurrence after liver transplantation (OLT), based on a monoclonal antibody able to recognise both wild-type and mutant HBsAg. Pre- and post-transplant samples from 22 patients transplanted for HBsAg positive cirrhosis were studied: Group A: 12 patients who reinfected the graft despite receiving HBIG; Group B: 6 patients with no HBV recurrence with continuous HBIG; Group C: 4 patients with HBV recurrence without prophylaxis. By running the new assay in parallel with an immunoassay that is susceptible to HBsAg mutants, 4 of 12 cases were identified in Group A with HBV recurrence due to surface antibody escape mutants, whereas in 8 patients this was due to the wild-type HBV. The results from the immunoassays were confirmed in all cases by HBV DNA sequencing. The surface gene mutations in the 4 patients affected codons 144 and 145 and in one of these 4 patients HBV strains with mutations in both codons were detected before and after transplantation. The epitope recognised by the new monoclonal antibody that reacts with both wild-type and mutant HBsAg seems to remain stable in the HBIG-induced HBV mutants. This serological approach allows rapid and cost-effective screening for HBsAg escape mutants in the liver transplant setting and may be helpful in the selection of appropriate prophylaxis.

Novel immunoassay for the detection of hepatitis B surface 'escape' mutants and its application in liver transplant recipients

Hepatitis B virus (HBV) strains with mutations in the surface gene are responsible for the failure of prophylaxis with hepatitis B immunoglobulin (HBIG) in a proportion of patients transplanted for HBsAg positive cirrhosis. So far, the emergence and evolution of these 'surface antibody escape' mutants have been studied by DNA sequencing. In this study the use of an immunoassay is described for diagnosis and characterisation of HBV recurrence after liver transplantation (OLT), based on a monoclonal antibody able to recognise both wild-type and mutant HBsAg. Pre- and post-transplant samples from 22 patients transplanted for HBsAg positive cirrhosis were studied: Group A: 12 patients who reinfected the graft despite receiving HBIG; Group B: 6 patients with no HBV recurrence with continuous HBIG; Group C: 4 patients with HBV recurrence without prophylaxis. By running the new assay in parallel with an immunoassay that is susceptible to HBsAg mutants, 4 of 12 cases were identified in Group A with HBV recurrence due to surface antibody escape mutants, whereas in 8 patients this was due to the wild-type HBV. The results from the immunoassays were confirmed in all cases by HBV DNA sequencing. The surface gene mutations in the 4 patients affected codons 144 and 145 and in one of these 4 patients HBV strains with mutations in both codons were detected before and after transplantation. The epitope recognised by the new monoclonal antibody that reacts with both wild-type and mutant HBsAg seems to remain stable in the HBIG-induced HBV mutants. This serological approach allows rapid and cost-effective screening for HBsAg escape mutants in the liver transplant setting and may be helpful in the selection of appropriate prophylaxis.

Extended routine polymerase chain reaction surveillance and pre-emptive antiviral therapy for cytomegalovirus after allogeneic transplantation

Pre-emptive treatment strategies based on sensitive screening for cytomegalovirus (CMV) infection up to day +100 after allogeneic transplantation have been shown to reduce the incidence of CMV disease during the period of surveillance. However, the use of ganciclovir has been associated with delays in immune reconstitution and an increased incidence of late CMV disease after day +100. In the present study, 81 patients undergoing allogeneic transplantation received polymerase chain reaction (PCR)-guided pre-emptive therapy based on detection of CMV DNA by PCR on 2 consecutive weeks up to day +180. Thirty-three of the 52 high-risk patients (CMV-seropositive donor or recipient) received a total of 45 treatment episodes up to day +100. Three of these patients (5.7%) developed CMV disease, with one fatality. Twelve of the surviving 44 high-risk patients (27%) required pre-emptive treatment between days +101 and +192, but none of these patients developed late CMV disease with a median follow-up of 402 d (range 117-952 d). Antiviral therapy was stopped after a single negative PCR result with no subsequent episodes of CMV disease while patients remained off antiviral treatment. As all initial episodes of CMV DNA detection occurred within 60 d of transplantation, it may be possible to discontinue monitoring beyond day +100 in patients who have remained CMV PCR negative before this. Thus, we have confirmed that PCR-guided pre-emptive therapy results in a low incidence of CMV disease before day +100 and that discontinuing treatment on the basis of viral clearance as determined by CMV PCR appears to be safe practice. In addition, we have observed no episodes of late CMV disease with an extension of surveillance to 26 weeks.

Effects of handling and storage of blood on the stability of hepatitis C virus RNA: implications for NAT testing in transfusion practice

BACKGROUND AND OBJECTIVES

To determine the stability of hepatitis C virus (HCV) RNA during transport and storage of blood samples from donors, prior to screening for HCV by nucleic acid amplification technology.

MATERIALS AND METHODS

Various blood and plasma sample types were stored for up to 120 h at different temperatures and the HCV RNA level was measured using an in house quantitative reverse transcription-polymerase chain reaction.

RESULTS

No decline in HCV RNA level was observed after 72 h of storage of whole blood at 4 degrees C in EDTA tubes (Greiner) and Plasma Preparation Tubes (PPT; Becton Dickinson), while insignificant declines of 0.2 log10 and 0. 25 log10 occurred at 25 degrees C after 72 h in the EDTA tubes and PPT tubes, respectively. When whole blood was stored with mixed anticoagulants CPDA-1 and EDTA for up to 120 h, no decline in HCV RNA level was observed at 4 degrees C and 25 degrees C, while a significant decline of 0.37 log10 occurred at 37 degrees C after 120 h. The temperature during transportation was investigated with a 12-hour period at 25 degrees C and 37 degrees C before storage at 4 degrees C for 108 h. Neither temperature resulted in any loss of HCV RNA in comparison with 120 h of storage at 4 degrees C.

CONCLUSION

Whole blood anticoagulated with EDTA or CPDA-1/EDTA may be stored at up to 25 degrees C (room temperature) for up to 5 days without any significant loss in plasma HCV RNA level.