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B C Dow

Publications and source records attributed to B C Dow.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of prevalence rates of microbiological markers between bone/tissue donations and new blood donors in Scotland.

BACKGROUND AND OBJECTIVES: Blood-borne virus prevalence rates of samples accompanying tissue donors are not widely available. This article compares the rates in Scottish bone/tissue donors with those of new blood donors for the 7-year period, 1998-2004. MATERIALS AND METHODS: Data were collated from existing internal reports. Age distributions of the donor populations were obtained by extracting information from existing computer databases. RESULTS: Scottish bone/tissue donors were found to have a fourfold higher prevalence for hepatitis B virus (HBV), a 1.6-fold higher prevalence for hepatitis C virus (HCV), an 11-fold higher prevalence for human T-cell lymphotropic virus (HTLV) and a 34-fold higher prevalence for syphilis compared with new blood donors. Excluding confirmed positives, the repeat-reactive rates for bone/tissue donors were similar to those of new blood donors. CONCLUSIONS: The data demonstrated that the prevalence of blood-borne viruses in Scottish bone/tissue donors is higher than in new blood donors. We believe that the different age profiles of the two donor populations plays a significant role.

Antibodies, Bacterial↗
PubMed2006

Detection of HTLV-I and -II in Scottish blood donor samples and archive donations.

BACKGROUND AND OBJECTIVES: Positive samples identified during routine serological screening for HCV (hepatitis C virus), HBV (hepatitis B virus) and HIV (human immunodeficiency virus) are confirmed by nucleic acid testing in the SNBTS (Scottish National Blood Transfusion Service) PCR Reference laboratory. Serological screening for HTLV-I (human T-cell lymphotropic virus type I) and -II was implemented in Scotland in November 2002, at which time a PCR assay was not available for confirmation. Our aim was to develop a real-time PCR assay that could be used for the confirmation of samples showing HTLV-I serological positive or indeterminate reactivity and to investigate whether a serologically silent carrier status exists ('Tax' only) in the Scottish donor population. MATERIALS AND METHODS: A real-time HTLV PCR was devised using a lymphoblastoid cell line which has HTLV-I sequence integrated in the genome (C8166 cells). These were spiked into peripheral blood mononuclear cells. The assay was evaluated on archived serologically confirmed HTLV-positive samples and new positives identified since implementation of screening. RESULTS: HTLV-I and -II were detected in cells and plasma from stored donations and a serological positive donation identified in routine screening. HTLV DNA can also be amplified from the plasma obtained from plasma preparation tubes. There was no evidence of a carrier status ('Tax' only) in 100 serologically negative blood donors tested. The PCR assay developed is reliable and sensitive, capable of identifying one copy of HTLV-I. CONCLUSIONS: The HTLV PCR is a useful addition for HTLV confirmation, especially in serologically indeterminate samples and for look-back studies. HTLV PCR confirmation will provide additional useful information for donor medical staff for counselling donors.

Blood Donors↗
PubMed2005

Hepatitis B virus genotypes and precore mutations in Scottish blood donors.

BACKGROUND AND OBJECTIVES: This study was carried out to determine the frequency of hepatitis B virus (HBV) core promoter variants (nucleotide positions 1762, 1764) and precore variants (nucleotide position 1896) in hepatitis B surface antigen (HBsAg)-positive Scottish blood donors. HBV genotypes present in this population were also identified. MATERIALS AND METHODS: A total of 85 HBsAg-positive blood donor samples were included in the study. Of these, 79 were polymerase chain reaction (PCR) positive and had sequence and mutation information. They were divided into two groups: group 1 (23 individuals) were hepatitis B e antigen (HBeAg)-positive and negative for antibody to HBe (anti-HBe); and group 2 (56 individuals) were HBeAg negative and positive for anti-HBe. A line probe assay was used to detect mutations, and a comparison was made by using direct sequence analysis. A different line probe assay was used to identify HBV genotype. RESULTS: The frequencies of mutations in group 1 were 22% each for mutations 1762, 1764 and 1896, increasing to 26%, 35% and 55% in group 2, respectively. By contrast, direct sequence analysis failed to identify 70% of wild-type/mutant mixes. The prevalence of viral genotypes was 41% for genotype A, 12% for genotype B, 5% for genotype C, 30% for genotype D and 12% for mixed-genotype infections. Precore mutations were seen in 10%, 88%, 25% and 74% of genotypes A, B, C and D, respectively. CONCLUSIONS: The results indicate that core promoter and/or precore mutants may be under-reported. The combination of HBV PCR and line probe assays is useful for supplementing HBV serological tests. Non-Caucasian genotypes are present in the UK blood-donating population and will therefore affect the demographics of HBV infection.

Blood Donors↗
PubMed2005

Detection of HCV and HIV-1 antibody negative infections in Scottish and Northern Ireland blood donations by nucleic acid amplification testing.

BACKGROUND AND OBJECTIVES: To reduce the risk of transfusion-transmissible viruses entering the blood supply, the nucleic acid amplification testing (NAT) was implemented to screen Scottish and Northern Irish blood donations in minipools. After 5 years of NAT for hepatitis C virus (HCV) and 2 years for human immunodeficiency virus-1 (HIV-1), the yield of serologically negative, nucleic acid positive 'window donations' and cost-benefit of NAT is under review. MATERIALS AND METHODS: When the Scottish National Blood Transfusion Service (SNBTS) implemented NAT in 1999, a fully automated 'black box' system was not available. Therefore, an 'in-house' assimilated NAT assay was developed, validated and implemented. The system is flexible and allows testing for additional viral markers to be introduced with relative ease. RESULTS: The HCV and HIV NAT assays have 95% detection levels of 7.25 IU/ml and 39.8 IU/ml, respectively, as determined by probit analysis. One HCV (1 in 1.9 million) and one HIV (1 in 0.77 million) window donation have been detected in 5 and 2 years, respectively, of NAT. CONCLUSION: The SNBTS NAT assays are robust and have performed consistently over the last 5 years. The design of the in-house system allowed HIV NAT to be added in 2003 at a relatively small additional cost per sample, although for both assays, the royalty fee far exceeds the cost of the test itself. Clearly NAT has a benefit in improving the safety of the blood supply although the risks of transfusion-transmitted viral infections, as reported in the Serious Hazards of Transfusion (SHOT) report, are extremely low. Also, in UK the yield of HCV antibody negative, NAT positive donations is far lower than predicted although the early detection of an HIV window period donation and the increase of HIV in the blood donor and general populations may provide a stronger case for HIV NAT. SUMMARY SENTENCE: The yield of HCV and HIV NAT in UK is significantly less than that anticipated from statistical models.

Adult↗
PubMed2004

Acute hepatitis C virus seroconversion in a Scottish blood donor: HCV antigen is not comparable with HCV nucleic acid amplification technology screening.

BACKGROUND AND OBJECTIVES: This study was conducted to analyse the usefulness of hepatitis C virus (HCV) core antigen tests for the confirmation of HCV infection in a donor presenting as nucleic acid amplification technology (NAT) positive but negative for antibodies to HCV (anti-HCV). MATERIALS AND METHODS: Blood donations were screened, in parallel, for anti-HCV using the Abbott PRISM HCV Chemiluminescent immunoassay (ChLIA) and an 'in-house' HCV NAT (pools of up to 95 donations). An HCV NAT-positive antibody-negative donor was identified. Twelve follow-up samples were obtained and tested with various HCV antigen (including the recently marketed Trak-C second-generation assay) and HCV antibody assays. RESULTS: The single HCV NAT-positive, antibody-negative donation was identified from 1 117 681 donations screened in the 4-year period, July 1999 to June 2003. The index donation was positive by Ortho HCV core antigen enzyme immunoassay (EIA) and Ortho Trak-C (second-generation HCV core antigen EIA). An archive sample, taken 127 days prior to the index donation, was negative for all HCV markers. Subsequent samples demonstrated a loss of reactivity in the Ortho HCV core antigen EIA and reduced activity in the Ortho Trak-C until day 69. Immunoblot (Ortho RIBA-3) and HCV PRISM became positive on day 62, whilst Ortho HCV ELISA was not positive until day 132 or Biorad HCV ELISA until day 160. An alternative immunoblot (Innogenetics Innolia III) was positive from day 55. RNA levels fluctuated considerably during the follow-up period, being completely undetectable by routine screening methods at the time-point around seroconversion; subsequently, antibody was detected using all assays investigated. CONCLUSIONS: This HCV-converting blood donor provided a unique panel of samples for using to assess current (and future) HCV assay systems. The overall test results led to the conclusion that individual HCV antigen testing should not be considered as equivalent to HCV NAT minipool screening. Trak-C antigen testing may be considered as a suitable confirmatory assay for isolated HCV NAT reactivity.

Acute Disease↗
PubMed2002

Hepatitis B vaccinees may be mistaken for confirmed hepatitis B surface antigen-positive blood donors.

BACKGROUND AND OBJECTIVES: Hepatitis B surface antigen (HBsAg) test sensitivities have gradually increased, and neutralizable weak HBsAg-positive donations, with no other hepatitis B virus (HBV) markers, have occasionally been found in our donor population. On investigation, these donors have admitted to receiving hepatitis B vaccine up to 5 days previously. A study was therefore initiated to monitor HBsAg reactivity amongst volunteers after receiving their first dose of hepatitis B vaccine. MATERIALS AND METHODS: Eight volunteers were tested using three HBsAg assays (Abbott Auszyme, Ortho HBsAg-3 and Abbott/Murex GE34/36) on days 0, 3, 5, 7 and 10 after administration of hepatitis B vaccine. RESULTS: Two HBsAg tests (Abbott Auszyme and Ortho HBsAg-3) did not detect HBsAg reactivity amongst the volunteers, although the Abbott Auszyme test results reached 70-80% of the manufacturer's cut-off at day 3 in two volunteers. The most recently launched assay (Abbott/Murex GE 34/36) detected seven (87%) of the eight volunteers as HBsAg reactive on day 3, and two (25%) volunteers were still reactive on day 5. CONCLUSION: The Abbott/Murex GE 34/36 assay demonstrated HBsAg reactivity in most volunteers on day 3 and in some on day 5 after vaccination. It is therefore recommended that individuals who have recently been vaccinated with hepatitis B be deferred from blood donation for at least 7 days.

Blood Donors↗
PubMed2002

Transfusion-transmitted hepatitis B virus infection in the UK: a small and moving target.

BACKGROUND AND OBJECTIVES: Transfusion-transmitted hepatitis B virus (TT-HBV) infections, when analysed in detail provide information about the nature and relative frequency of the sources of infectious donations. These cases are therefore used to inform blood safety strategies. This study updates previous reviews of the causes of TT-HBV in order to determine whether a change may have occurred in recent years. MATERIALS AND METHODS: Cases of TT-HBV reported during 1998-2001 were reviewed and the nature of the infectious donations described. These cases were compared to a previously published case series reported during 1991-97. RESULTS: Six cases of TT-HBV have been reported in the UK between 1998 and 2001. All were the result of infectious donations collected from donors with acute HBV infection. This is in contrast to the series reported during 1991-97 when only three of 14 similar cases were caused by acute infections in donors, with the majority of incidents being the result of chronic infection in donors. CONCLUSIONS: There appears to have been a change in the relative importance of acute and chronic HBV infection in blood donors in causing TT-HBV infections. Improvements in the sensitivity of HBsAg assays and/or a decrease in the prevalence of chronic HBV infection in blood donors could explain this observation. This change may have implications for strategies to reduce the risk of TT-HBV infection.

Acute Disease↗
PubMed2001

HTLV antibody screening using mini-pools.

At the present time, the UK blood transfusion services do not screen blood donations for anti-HTLV. This presentation describes a pilot study to ascertain the feasibility of HTLV antibody screening using mini-pools and also provides an estimate of HTLV prevalence within our donor population in Scotland and Northern Ireland. The Abbott/Murex HTLV I/II GE80/81 ELISA was selected for the trial. Thirty confirmed HTLV positive library samples were tested at various dilutions and five were shown to be nonreactive at a dilution of 1:100. Residues of mini-pools (of up to 95 individual donations) prepared for HCV NAT testing were tested with the Abbott/Murex GE80/81 assay. Of 6666 mini-pools (equivalent to 570 609 donations) tested, six were repeatedly reactive. All six mini-pools were confirmed HTLV antibody positive by line immunoassay. Four were confirmed to be HTLV-I positive, one HTLV-II positive and one HTLV positive (unable to type). Dilutions (1:100) of the five HTLV "nonreactive" positive samples were included in each test plate and used to determine a grey-zone cut-off. Using this grey-zone system an additional six (0.09%) mini-pool samples gave repeatedly reactive grey-zone results, none of which were confirmed. The minimum Scottish/Irish HTLV donor prevalence was shown to be 1:95 000.

Blood Donors↗
PubMed1999

Antigenic characterization of pre- and post-liver transplant hepatitis B surface antigen sequences from patients treated with hepatitis B immune globulin.

BACKGROUND/AIMS: The success of treatment with hepatitis B hyperimmune globulin in preventing recurrence of hepatitis B virus infection in patients undergoing orthotopic liver transplantation depends on maintaining levels of anti-HBs sufficient to neutralise hepatitis B virus and also on patient compliance. Breakthrough infections may occur, and these have been associated with the emergence of variants in HBsAg. METHODS: Three patients, two who relapsed and one who had no evidence of hepatitis B virus infection post-orthotopic liver transplantation were studied. Polymerase chain reaction and sequencing of pre- and post-orthotopic liver transplantation samples was followed by antigenic analysis of the in vitro expressed cloned sequences. RESULTS: In two patients who were treated with hyperimmune globulin, amino acid variation in the region of the immunodominant B cell epitopes of HBsAg occurred. Sequencing of clones revealed fluctuating variant sequences over time. One had clinical relapse and immune escape was evident on in vitro antigenic analysis. Patient two lost HBsAg reactivity post-orthotopic liver transplantation. There was loss of an antigenically critical cysteine molecule; sequencing of clones revealed that this was the dominant species. The third patient relapsed when protective levels of anti-HBs were not maintained; HBsAg showed no variation compared to a standard subtype sequence. CONCLUSION: These data provide strong experimental evidence of immune escape. It appears that hyperimmune globulin provides the selection pressure. In these patients, HBsAg negativity does not exclude infection of the transplanted liver.

Aged↗
PubMed1999

Microbiology confirmatory tests for blood donors.

Blood donations collected in Scotland are currently screened for the presence of HBsAg, anti-HIV 1 + 2, anti-HCV and syphilis antibodies. Approximately 1% of all donations are found to repeatedly react to one of these four markers on screening but very few represent true infection. These samples must be sent to the designated confirmatory laboratory whose main role is to identify the true positive amongst a sea of 'false positives'. A battery of tests is used for this purpose, usually applied in a defined sequence. The use of such 'confirmatory algorithms' for each marker has been developed by most countries over the years and is now essential to the confirmatory process. The advent of gene amplification techniques such as PCR for initially pooled and eventually single donation testing will be the next challenge for confirmatory laboratories and will demand standards of confirmation as accurate as currently performed with the present serological markers.

Algorithms↗
PubMed1998

Use of PCR in resolving diagnostic difficulties potentially caused by genetic variation of hepatitis B virus.

AIMS: To assess the relevance of genetic variants of hepatitis B virus (HBV) and to demonstrate the usefulness of the polymerase chain reaction (PCR) in cases of HBV diagnostic difficulty. METHODS: Five serum samples from patients that presented diagnostic difficulty in routine laboratories were sent to a research laboratory for PCR, and if appropriate, S gene sequencing, in vitro expression, and antigenic analysis. RESULTS: The demonstration of HBV in serum by PCR allowed a definitive diagnosis of current infection. One serum sample with poor reactivity in a diagnostic assay had a minor hepatitis B surface antigen (HBsAg) variant and another with very poor reactivity had multiple variants of HBsAg. Transient HBsAg reactivity was observed in a recently vaccinated patient. A hepatitis Be antigen (HBeAg) false positive reaction was noted in a patient from a well defined risk group for HBV. One patient who was strongly HBsAg/HBeAg positive, but anti-hepatitis B core antibody negative, was viraemic. CONCLUSIONS: PCR may become the gold standard for the diagnosis of current HBV infection. HBV variants are responsible for a proportion of diagnostically difficult cases. Modification of commercial assays is necessary to increase the sensitivity of detection of such variants.

Adult↗
PubMed1996

Influence of viraemia and genotype upon serological reactivity in screening assays for antibody to hepatitis C virus.

Detection of antibody to recombinant proteins derived from hepatitis C virus (HCV) genotype 1 represents the principal method for diagnosis of HCV infection. A method was developed for quantifying antibody reactivity in two third-generation enzyme immunoassays (Ortho EIA 3.0 and Murex VK48), and the influence of viraemia, HCV genotype, and host factors such as age, gender, and risk group upon antibody levels were investigated in a consecutive series of 117 anti-HCV-positive volunteer blood donors. Viraemic donors (as assessed by the polymerase chain reaction; PCR) showed significantly higher levels of anti-HCV by the Ortho EIA than those who were nonviraemic (adjusted mean difference of 10.1 fold after multiple regression analysis). The only other factor to influence significantly antibody level was genotype, where it was found that donors infected with type 1 showed 4 to 4.5 times greater serological reactivity by the Ortho assay than those infected with type 2 or 3. Antibody levels by the Ortho assay correlated closely to those detected by the Murex VK48 assay, and similar differences between PCR-positive and negative donors and between those infected with different genotypes were found. Differences in serological reactivity between genotypes indicate that a large proportion of epitopes of the type 1a or 1b recombinant proteins used in current assays are genotype specific. Variation in sensitivity of screening assays for different genotypes is of potential concern when used in countries where non-type 1 genotypes predominate in the blood donor or patient population.

Alanine Transaminase↗
PubMed1996

Relevance of RIBA-3 supplementary test to HCV PCR positivity and genotypes for HCV confirmation of blood donors.

HCV antibody screening of 624,910 blood donations resulted in 3,832 samples being referred for confirmation. All were tested by RIBA-3 with 2,710 negative, 945 indeterminate and 177 positive results. HCV RNA was detected by PCR in an average of 69.5% of RIBA-3 positives (4 bands 84.1%; 3 bands 74.1%; 2 bands 34.1%) and only 0.53% of RIBA-3 indeterminates. Eighty-four percent of samples with a total RIBA-3 band intensity score (maximum 16) of > or = 8 were PCR positive compared with only 22% of those with a score of < 8. Total mean band intensities for HCV genotype 1 samples (n = 65) were 13.2, genotype 2 (n = 17) 11.4 and genotype 3 (n = 65) 11.2 with type 1 samples showing greater reactivity with c100 and c33 antibodies. No PCR positive type 1 samples were found with RIBA-3 total band scores less than 8, no PCR positive type 2 samples less than 6, whilst PCR positive type 3 samples were found with scores as low as 2. NS5 indeterminates were the most common (40.2%) single band pattern but yielded no PCR positive samples, followed by c33 (23.3%) with one PCR positive and c100 (20.2%) with one PCR positive whilst c22 indeterminates were least common (16.3%) but included three PCR positive donors. All five RIBA-3 indeterminate PCR positive donors were type 3.

Blood Donors↗