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Biomedical subjects

D R Howell

Publications and source records attributed to D R Howell.

At least 19 recordsLinked to original sources
PubMed2000

Retrospective follow-up of recipients and donors of blood donations reactive for anti-HBc or for single HCV antibodies.

A retrospective study was undertaken to investigate the infectivity of blood donations that were HCV RIBA indeterminate or reactive for 'anti-HBc only'. Samples from 6032 blood donations were tested for anti-HBc; 17 of them were positive for anti-HBc but were negative when tested for anti-HBs. None of the recipients of the red cells from these donations, when tested 9 months after transfusion, had evidence of HBV infection. Samples from 3000 blood donations were tested for HCV antibodies using RIBA-3; 53 had single lines. Samples taken 9 months after transfusion from the recipients of the red cells from these donations were tested for evidence of infection with hepatitis C, and all were negative.

Blood Donors↗
PubMed1998

Hepatitis B virus infection in patients attending a genitourinary medicine clinic: risk factors and vaccine coverage.

BACKGROUND: The hepatitis B virus (HBV) immunisation policy in the United Kingdom includes offering vaccines selectively to those at risk by sexual contact. Among genitourinary medicine (GUM) clinic attenders, homosexual men are offered vaccine, but estimates of the vaccine uptake are required to monitor policy and estimate the possible impact on transmission; heterosexuals are not routinely offered vaccine, but this policy might change if the prevalence was found to be high. OBJECTIVE: To determine the prevalence of HBV infection and vaccine uptake among patients attending a GUM clinic. METHODS: HBV seroprevalence determined by unlinked anonymous testing of consecutive blood samples sent for syphilis serology. Demographic and risk factor data and history of HBV immunization extracted from clinic notes before unlinking. Prevalence data were compared with a population of first time blood donors from the same area. SETTING: Open access GUM clinic in central London. RESULTS: Samples were obtained and tested from 441 homosexual and 527 heterosexual men and from 821 women over a 4 month period in 1990. After exclusion of injecting drug users and their sexual partners (n = 30) and HBV carriers attending for follow up (n = 12), the prevalence of antibody to HBV core (anti-HBc) was 38.7% in homosexual men, 5.9% in heterosexual men, and 3.5% in women (50.0%, 6.0%, 3.7% respectively if previous vaccinees were also excluded). The prevalence of HBV surface antigen positivity was 4.2%, 0.60%, and 0.39% respectively after exclusion of vaccinees (chi(2) p < 0.001 for homosexual men versus others). The prevalence of the anti-HBc in first time blood donors was 1.1% (8/749). Among male GUM clinic attenders, the prevalence of anti-HBc was higher in those of non-UK origin or place of birth and/or non-white ethnicity (odds ratios 2.87, 95% CI 1.57-5.24 and 8.06, CI 3.39-19.1, in homosexuals and heterosexuals respectively). In homosexual men anti-HBc prevalence increased with age (OR 1.05, CI 1.02-1.07 for each year) and lifetime number of STDs (OR 6.36, CI 3.77-10.8 for > or = 2 versus < 2) and in clinic reattenders compared with new patients (OR 5.42, 95% CI 3.32-9.16). Among heterosexuals, age was associated with anti-HBc prevalence in women (OR 1.09, CI 1.04-1.12) but not men (OR 0.99, 95% CI 0.95-1.02). There were no other associations in heterosexuals. A history of HBV immunisation in homosexual men was recorded in 13/131 (9.9%) of new patients and 103/305 (33.8%; OR 4.63, CI 2.49-8.60) clinic reattenders. CONCLUSIONS: Although higher than a sample of blood donors, the prevalence of serological markers of HBV infection among heterosexuals was low, providing little support for extending HBV immunisation to all heterosexuals attending GUM clinics as a targeted strategy for control of HBV infection. Homosexual men remain at high risk of infection, but many are now being immunised. Efforts to improve compliance with existing vaccine policies in GUM clinics should be encouraged.

Adult↗
PubMed1991

Low incidence of non-A, non-B post-transfusion hepatitis in London confirmed by hepatitis C virus serology.

To see whether the introduction of screening tests for post-transfusion non-A, non-B hepatitis (NANBH) in the UK would be worth while, the incidence of such hepatitis was assessed among patients receiving blood during operations at five hospitals served by the North London Blood Transfusion Centre. 387 patients, who each received blood or blood components from an average of 3 donors were followed up prospectively and blood samples were taken every 2 weeks for 3 months and then each month for a further 3 months. 229 patients also provided a sample at 12 months. All available patient and donor samples were tested for alanine aminotransferase concentrations and for antibody to hepatitis C virus (anti-HCV) by ELISA. Repeatedly anti-HCV positive samples were submitted to supplementary HCV assays. 1 of the 387 patients showed biochemical evidence of acute post-transfusion NANBH after exclusion of non-viral causes. Anti-HCV developed in this patient and the seroconversion was confirmed by recombinant immunoblot assay and polymerase chain reaction. Serum from 1 of the 8 donors whose blood he received was positive for anti-HCV by all three methods. In another patient HCV seroconversion was shown by ELISA but alanine aminotransferase concentrations remained normal throughout follow-up. His samples and those of his 2 donors were negative for HCV by the polymerase chain reaction. A third patient showed rises in alanine aminotransferase compatible with post-transfusion NANBH, but serology and polymerase chain reaction assays for HCV were negative for her samples and those of her donors. Anti-HCV reactivity likely to be false positive (negative by both confirmatory tests and no adverse effects in recipients) was seen in 6 of 1283 donors. This study, despite its being carried out in the part of the UK with the highest frequency of infectious markers in blood donations, has shown a very low incidence of post-transfusion NANBH.

Acute Disease↗
PubMed1991

Antibody to hepatitis C virus in blood donors found positive for other agents. I. Treponemal infection.

Stored serum samples from 169 blood donors found positive for TPHA were tested for antibodies to hepatitis C virus (anti-HCV) and to hepatitis B core (anti-HBc), as evidence of previous HBV infection, a condition known to be sexually transmissible. Only three donors were positive with a 'first generation' anti-HCV and all three failed to confirm with a recombinant immunoblot assay (RIBA). In contrast, 33 (19.5%) of the TPHA-positive donors were positive for anti-HBc. The results suggest that sexual transmission is not a major factor in the spread of HCV.

Blood Donors↗
PubMed1991

Anti-HIV-1: extended validation of a modified gelatin particle agglutination assay, and its use with an image analyser.

Modification of a commercial gelatin particle agglutination assay for anti-HIV-1 (MAT) has increased sensitivity, reduced reaction time and lowered the cost by 90%. We tested over 10,000 blood donations in parallel with the ELISA currently in use, and found the modified test to be highly sensitive and to enhance cost-effectiveness as it substantially reduces false-positive rates. The patterns of agglutination are clearly reproducible and readable by the naked eye and/or Image Analyzer, which provides objectivity and hard-copy documentation of results.

Agglutination Tests↗
PubMed1989

Rapid transfer of small volumes of serum into microplates.

A method has been devised to transfer small volumes of serum, as an adjunct to larger volume sampling, into microplates. The Costar Transplate 96 machine is used routinely in our laboratory for transferring serum samples into reaction wells for anti-HIV screening. Using this additional method a mean of 4 microliters of serum was transferred, within acceptable limits of error (coefficient of variation, c.v., 16%).

Agglutination Tests↗
PubMed1981

Contrasting patterns and frequency of antibodies to the surface, core, and e antigens of hepatitis B virus in blood donors and in homosexual patients.

An attempt was made to assess the significance of the relatively frequent low-titre positive reactions in radioimmunoassays for antibody to hepatitis B surface antigen. Serum specimens negative for surface antigen were assayed for antibodies to the surface, core, and e antigens of the Hepatitis B virus. Two populations were studied - one of low hepatitis B incidence (2000 blood donors) and one of high incidence (200 male patients attending a clinic for sexually transmitted diseases). The validity of some singly occurring low-titre anti-HBs and anti-HBc reactions is questioned, and the occurrence of positive reactions unrelated to previous hepatitis B infection inferred.

Antibodies, Viral↗
PubMed1980

A sensitive immunoradiometric assay for the detection of hepatitis B surface antigen.

A solid-phase immunoradiometric assay for hepatitis B surface antigen is described which has been in use since 1971. Initially it was used for reference laboratory work, but from 1974 it has also been used for screening blood and blood products. Methods for the production of reagents and their use in blood transfusion and reference work are outlined.

Blood Donors↗
PubMed1979

The 2', 3'-cyclic AMP 3'-phosphohydrolase in normal and psoriatic epidermis.

The activity of the enzyme 2', 3'-cyclic AMP 3'-phosphohydrolase is significantly greater in the 'involved' psoriatic skin than in the 'uninvolved' psoriatic skin or in skin samples taken from persons having clinically normal skin. Although the physiological function of this enzyme is not established, it is possible that, besides being associated with myelin, it may also play some role in cell proliferation and maturation, probably at the membrane level.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗