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Biomedical subjects

J A Barbara

Publications and source records attributed to J A Barbara.

At least 55 records · Page 3Linked to original sources
PubMed1996

Yersinia enterocolitica transmission from a red cell unit 34 days old.

In 1993 the North London Blood Transfusion Centre received its first report of Yersinia enterocolitica transmission from a unit of red cells supplied to a local hospital. The recipient was a 23-year-old male who was neutropenic following a third cycle of chemotherapy for treatment of acute myeloblastic leukaemia (FAB type M6) and received a 34-day-old red cell unit. During transfusion the patient developed septicaemia and endotoxin-mediated shock. The transfusion was stopped immediately and broad spectrum antibiotics administered immediately on suspicion of bacteraemia from the transfused unit. This prompt action undoubtedly prevented a fatal outcome. Y. enterocolitica was isolated from the blood bag. Antibody was also detected in the bag and in a sample taken from the donor 39 days post-donation. Antibody to serotype 03 was identified, the commonest serotype reported in transfusion-transmitted Y. enterocolitica. The donor reported no gastrointestinal upset or illness prior to donation. This transfusion reaction might not have occurred had the red cells been transfused earlier in their storage period, but would not have been prevented by the exclusion of donors with a history of gastrointestinal illness as the donor was asymptomatic. Nor would it have been prevented by inspecting the blood for a change in colour, as no such change was observed. Y. enterocolitica is a significant problem in transfusion medicine and transmission is generally associated with a high mortality rate. Hospitals should be urged to investigate bacteriologically all appropriate transfusion reactions so that the true extent of the problem in the United Kingdom can be assessed.

Adult↗
PubMed1996

Safety and efficacy of hepatitis C virus antibody screening of blood donors with two sequential screening assays.

BACKGROUND: Reactive samples in hepatitis C virus (HCV) antibody screening of blood donors are currently referred for a confirmatory assay. This scheme is not optimally efficient and is expensive because of the lack of specificity and cost of confirmatory tests, as well as the need to discard false-positive donations. As in some human immunodeficiency virus antibody-confirmatory schemes, the safety and efficacy of confirming anti-HCV with two sequential screening assays were evaluated. STUDY DESIGN AND METHODS: Three combinations of two anti-HCV screening assays were used to test 75,874 blood donors. Results were compared with the routine testing scheme and HCV RNA detection in any enzyme immunoassay-repeatably reactive samples. RESULTS: The use of an alternative screening assay for repeat testing decreased the proportion of enzyme immunoassay-positive donors from 0.28 to 0.05 percent. All samples that were "confirmed" as positive by the standard combination of immunoassays and all HCV RNA-positive samples were detected by the sequential screening assays. No samples that had discordant results on primary and secondary screening assays were confirmed by recombinant immunoblot assay or were found to contain detectable HCV RNA. CONCLUSION: The combination of screening assays for anti-HCV confirmation was as safe as, cheaper than, and nearly as efficient as the standard testing scheme.

Blood Donors↗
PubMed1995

Confidential unit exclusion: the North London Blood Transfusion Centre's experience.

A 'Confidential AIDS Questionnaire' has been used at North London Blood Transfusion Centre (NLBTC) donor sessions since July, 1985. The aim of the questionnaire is to encourage self-exclusion by those donors whose behaviour puts them at risk of HIV infection. In a situation where such individuals cannot avoid donating they can indicate, in confidence, that their blood should not be used for transfusion. Since the introduction of this procedure, an average of 10 donors per month, who admitted relevant risk behaviour, have been permanently excluded and a number of prospective donors have excluded themselves when faced with the questionnaire. We have found the questionnaire to be well accepted by donors. It is a useful adjunct to routine donor selection and microbiological testing of donations in our efforts to minimize transfusion-transmitted infection.

Acquired Immunodeficiency Syndrome↗
PubMed1995

A multicentre assessment of the specificity of ten anti-HBc screening tests.

Samples from 1828 donations were screened for anti-HBc at seven sites in the UK using kits supplied by 10 manufacturers. Only 10 (0.55%) donations were considered to have true anti-HBc reactivity and these were detected by all 10 kits. Additional markers of HBV infection were found in nine of these 10 donations. Additional reactives were found by all kits, the number ranging from 1 to 43. In the four more specific kits, the 10 true reactives were clearly distinguished from the 'false reactives' by the strength of the reaction. It is concluded that the reliance on a single ELISA test for anti-HBc diagnosis is unwise. The use of a second test known to be more specific than the screening ELISA is recommended.

Blood Donors↗
PubMed1994

Dissociation of TNF-alpha cytotoxic and proinflammatory activities by p55 receptor- and p75 receptor-selective TNF-alpha mutants.

Human tumour necrosis factor alpha (TNF-alpha) is a pleiotropic cytokine capable of killing mammalian tumour cells in vitro and in vivo, and of enhancing the proinflammatory activity of leucocytes and endothelium, the latter effects limiting its usage as an antitumour agent in humans. Using TNF-alpha mutants with a selective capacity to bind to the TNF p55 receptor (TNFR55) or to the p75 receptor (TNFR75) we show here that these two major activities of TNF-alpha can be dissociated. The TNFR55-selective mutants (R32W, E146K and R32W-S86T) which bind poorly to TNFR75 displayed similar potency to wild-type TNF in causing cytotoxicity of a human laryngeal carcinoma-derived cell line (HEp-2) and cytostasis in a human leukaemic cell line (U937). However, these TNFR55-selective mutants exhibited lower proinflammatory activity than wild-type TNF. Specifically, TNF-alpha's priming of human neutrophils for superoxide production and antibody-dependent cell-mediated cytotoxicity, platelet-activating factor synthesis and adhesion to endothelium were reduced by up to 170-fold. Activation of human endothelial cell functions represented by human umbilical venular endothelial cell (HUVEC) adhesiveness for neutrophils, E-selectin expression, neutrophil transmigration and IL-8 secretion were also reduced by up to 280-fold. On the other hand, D143F, a TNFR75-selective mutant tested either alone or in combination with TNFR55-selective mutants, did not stimulate these activities despite being able to cause cytokine production in TNFR75-transfected PC60 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1994

A study of anti-hepatitis C positive blood donors: the first year of screening.

In the U.K., blood donations have been routinely screened for anti-HCV since September 1991. In order to get the most epidemiological benefit from these extensive screening data, the histories obtained at counselling from donors confirmed to be anti-HCV positive, 'indeterminate' and falsely positive have been analysed in detail. In addition, the associations with potential risk factors have been investigated by comparing these groups of donors with a control group of 771 routine donors bled on one day during the study, at North London Blood Transfusion Centre. This paper documents the prevalence and demography of HCV infection in asymptomatic blood donors, to assess various possible sources of infection and the association between liver function test results and alcohol consumption in donors. One in 1400 previously untested donors was confirmed positive for anti-HCV. Age (the group 30-49 years being highest), tattooing and intravenous drug use in both sexes, ear-piercing in males and blood transfusion in females were all significantly associated with an increased risk of HCV infection. Intravenous drug use proved to be the factor most strongly associated with risk. Liver function tests (alanine aminotransferase) were elevated in a significant number of donors confirmed to be anti-HCV positive but no clear correlation between alanine aminotransferase level and either time since infection or alcohol consumption was found. Alcohol consumption was significantly higher in donors confirmed to be anti-HCV positive and was particularly marked in those admitting to previous intravenous drug use.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Anti-HBc assays: evaluation of end-point sensitivity and performance.

The performance characteristics of eight commercially available anti-HBc assays-seven ELISAs and a modified haemagglutination assay-were assessed using an eight-sample panel of sera collected from blood donors representing a cross-section of anti-HBc-positive donors that might be expected to be encountered in the course of routine screening of blood donations. End-point sensitivity was investigated with a view to choosing one anti-HBc ELISA for use in a second phase routine donor screening study in parallel with the modified haemagglutination test. The chosen anti-HBc ELISA had to be of an acceptable sensitivity level in comparison with all the other ELISAs investigated, and the ease of use and overall test time had to be taken into account. With a view to this, although the Murex assay was by far the most sensitive, the test time with the protocol available at the time was too long and therefore the Biokit ELISA was chosen for the second phase.

Blood Transfusion↗
PubMed1993

Prevalence of antibodies to human T cell leukaemia/lymphoma virus in blood donors in north London.

OBJECTIVES: To determine the prevalence of antibodies to the human T cell leukaemia/lymphoma viruses (HTLV-I and HTLV-II) in blood donors in north London in order to assess the economic impact and the logistic effects that routine screening would have on the blood supply. DESIGN: All donations collected by the north London blood transfusion centre between January 1991 and June 1991 were screened for antibodies to HTLV-I and HTLV-II by modified, improved Fujirebio gel particle agglutination test. Positive samples were titrated and retested as necessary. SUBJECTS: 96,720 unpaid volunteers, who gave 105,730 consecutive donations of blood and plasma. SETTING: North London blood transfusion centre. MAIN OUTCOME MEASURE: Observed numbers of donors confirmed to be seropositive for HTLV by reference laboratories. RESULTS: Of 2622 (2.5%) initially reactive samples, 414 (0.4% of all samples) gave a titre of > or = 1 in 16 on the modified agglutination test. Thirty five of the 414 serum samples yielded positive results on one of two enzyme linked immunosorbent assays (ELISA (Cambridge Biotech and Abbot)), and none of these results were confirmed by either reference laboratory. Five samples yielded positive results on both ELISAs and all five of these were confirmed to contain antibodies to HTLV. One of the five contained antibodies to HTLV-II and the others antibodies to HTLV-I. Four seropositive donors were white women whose only risk factor for infection was sexual contact. The fifth (positive for antibodies to HTLV-II) was an Anglo-Caribbean man who admitted to previous misuse of intravenous drugs. CONCLUSION: The prevalence of antibodies to HTLV in blood donors in north London was one in 19,344 (0.005%). Up to 100 donors a year might be identified in the United Kingdom as being infected with HTLV, although prevalence in different regions may vary considerably.

Adult↗