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Biomedical subjects

P P Mortimer

Publications and source records attributed to P P Mortimer.

At least 19 recordsLinked to original sources
PubMed1995

GACPAT HIV 1 + 2: a simple, inexpensive assay to screen for, and discriminate between, anti-HIV 1 and anti-HIV 2.

A simple and cheap assay suitable for screening for anti-HIV 1 and anti-HIV 2 and discriminating between them was evaluated. In it specimens are incubated in U-bottomed microplate wells coated with anti-human IgG for 30 min at room temperature. After washing, 100 microliters of a 1 in 50 dilution of HIV 1-coated gelatin particles (Serodia-HIV 1/2, Fujirebio) are added. Settling patterns are read on the second day: A positive reaction is indicated by adherence of the particles and a negative by a button. The HIV 1 particles are then washed away and HIV 2 particles added. Anti-HIV 2 reaction patterns are read on the third day. To assess the performance of the modified "GACPAT HIV 1 + 2" assay a panel of 1,621 serum/plasma specimens was used. It comprised validated anti-HIV 1 positive (n = 220), anti-HIV 2 positive (n = 214), dual anti-HIV 1/anti-HIV 2 positive (n = 11), and anti-HIV negative (n = 1,176) serum/plasma specimens. All 434 specimens that contained anti-HIV 1 or anti-HIV 2 reacted positively with the homologous particles. The 11 dually positive specimens reacted positively with both HIV 1 and HIV 2 particles. Five (2.3%) anti-HIV 1 and five (2.3%) anti-HIV 2 positive specimens gave positive reactions with both particle types, but none of the five cross-reactive anti-HIV 2 specimens were dually reactive when the order of particle addition was reversed.(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS Serodiagnosis↗
PubMed1995

Evaluation of a combined HIV-1/2 and HTLV-I/II assay for screening blood donors.

A combined immunoassay for the simultaneous detection of antibodies to HIV-1/2 and HTLV-I/II (Bioelisa, Launch Diagnostics) has been evaluated to determine its suitability for routine use in blood screening. 84,222 donations were tested from 76,452 donors. One HIV- and 1 HTLV-1-positive donor were identified. The specificity was 99.7%, and the sensitivity for anti-HIV-1, anti-HIV-2, and anti-HTLV-1 on 173 positive sera was 100%; 2 of 25 anti-HTLV-II-positive sera were non-reactive. Although the specificity of the assay is not as high as that of HIV-1/2 kits currently in UK transfusion use, the information gained about donor HTLV antibody status makes the test an attractive alternative to them.

Blood Donors↗
PubMed1995

False negative results in enzyme linked immunosorbent assays using synthetic HIV antigens.

The sensitivity of 12 commonly used anti-HIV-1/HIV-2 enzyme immunoassays was evaluated. The assays, each of which utilises at least one synthetic HIV antigen, were tested against a panel of 1092 specimens previously designated anti-HIV positive. In a total of 13 104 tests there were eight false negative results attributable to assay insensitivity: three were on two serum samples collected close to seroconverison and five on another serum specimen. These eight false negative results arose in seven different assays. Five other false results were attributable to technical error. This false negativity rate indicates that all of the assays performed adequately and leads to an estimate of one false negative result in a thousand tests in routine diagnostic practice. Because of the antigenic heterogeneity of HIV strains, similar evaluations would be required in several regions before this satisfactory level of sensitivity in anti-HIV assays incorporating synthetic antigens could be said to be universal.

Enzyme-Linked Immunosorbent Assay↗
PubMed1995

Arsphenamine jaundice and the recognition of instrument-borne virus infection.

Soon after its introduction in 1910, intravenous arsphenamine treatment for syphilis was found to be complicated by jaundice. The underlying cause, unsterile syringes and needles, was eventually recognised in the early 1940s, mainly through the efforts of British Army investigators. The infection most often transmitted was probably hepatitis B virus (HBV), but the high mortality in a few of the outbreaks of arsphenamine jaundice suggests that variants of HBV, or other hepatitis viruses, were sometimes involved. Fifty years later, at a time when there are estimated to be over three hundred million carriers of HBV in the world and probably at least as many hepatitis C virus carriers, and when the World Health Organisation estimates that there have been 17 million infections with human immunodeficiency virus, the lessons learnt around 1945 about the need to use sterile instruments and needles for all injections and venepunctures remain highly pertinent.

Arsphenamine↗
PubMed1994

A lurking endemic.

Explore the source record for details and available documents.

Blood-Borne Pathogens↗
PubMed1992

Performance assessment of neonatal dried blood spot testing for HIV antibody.

A study was undertaken to assess the performance of laboratories participating in the UK unlinked anonymised neonatal screening programme for the detection of HIV antibody. A coded panel of 100 contrived dried blood spots prepared form well characterised anti-HIV-1 and anti-HIV-2 positive sera and an anti-HIV negative serum was distributed to eight testing centres. Fifty-one out of 52 anti-HIV-1 positive samples were identified by all eight laboratories: five laboratories identified all 52 specimens. Only one laboratory detected all four anti-HIV-2 positive spots. None of the laboratories reported a seronegative spot as reactive. The sensitivity of anonymised neonatal anti-HIV-1 screening was deemed satisfactory in all participating laboratories but the margin of sensitivity was insufficient to allow pooling of dried blood spot eluates before testing. Technical modifications would be necessary to increase sensitivity for anti-HIV-2 were HIV-2 infection to be reported more frequently in the UK. Performance assessment of the screening programme should be repeated at regular intervals.

AIDS Serodiagnosis↗
PubMed1992

The detection in urine specimens of IgG and IgM antibodies to hepatitis A and hepatitis B core antigens.

The use of urine as a noninvasive specimen for the diagnosis of hepatitis A (HAV) and hepatitis B (HBV) virus infections was investigated. Specimens of urine were collected at the same time as blood or saliva specimens, or singly in cases of previously serologically confirmed recent infection. The specimens were tested for IgG and IgM anti-HAV and anti-HBc by immunoglobulin class-specific capture radioimmunoassays (GACRIA and MACRIA). On the basis of assays on urine specimens it was possible to distinguish between individuals who were susceptible or immune to HAV or who had recently been infected with HAV. Using assays on 327 corresponding saliva specimens as reference tests, the observed sensitivity and specificity of tests on urine specimens by anti-HAV GACRIA were 98.9% and 99.1%, respectively, and by anti-HAV MACRIA were 95.8% and 99.6%, respectively. IgM and IgG anti-HBc were detected readily in the urine of 35 acute or recent cases of hepatitis B but were not found in the urine of seronegative individuals. Of the urine specimens from 52 individuals who were HBsAg carriers or who had had long past HBV infections, 49 contained detectable IgG anti-HBc. Of urine specimens from 42 HBsAg carriers, 11 contained raised IgM anti-HBc levels. Urine, which is a convenient specimen to collect, can be used to study outbreaks of hepatitis A, to ascertain the HAV immune status of individuals, to differentiate hepatitis A from hepatitis B, and to identify individuals who have been naturally exposed to HBV.

Hepatitis A↗
PubMed1992

Is the IEMA combined incubator/shaker device preferable to a waterbath for incubating enzyme immunoassays?

An incubator/shaker device proved to be a convenient alternative to a waterbath for the incubation of enzyme immunoassays (EIA). The device achieved effective and even heat transfer. In two of five EIAs it increased reactivity and in three of five EIAs it slightly increased the discrimination between seronegative and seropositive specimens though, for the samples investigated, extra sensitivity was not thereby achieved. At a high shaking frequency (1400 rpm) there was cross-contamination between wells, but this did not occur at 900 rpm. The relative contributions of heating and of shaking to the incubation of EIAs deserve further investigation.

AIDS Serodiagnosis↗
PubMed1992

Confirmation of second generation anti-hepatitis C virus enzyme immunoassays by antigenic cross-validation.

AIM: To determine if a scheme for validating enzyme immunoassay (EIA) results could be devised that did not require costly and methodically elaborate supplemental assays. METHODS: Samples (n = 525) from patients with haemophilia A, leukaemia, and chronic liver disease and at increased risk of hepatitis C virus infection were tested by EIA-1 (Ortho Diagnostics), an assay which uses recombinant HCV fusion proteins as antigens, and by EIA-2 (United Biomedical), an assay based on synthetic HCV oligopeptide antigens. RESULTS: Samples (n = 193) were repeatedly reactive in both EIAs. Of these, 190 (98%) yielded reactivities in both of two supplemental assays used, one an immunoblot assay (RIBA) using recombinant HCV polypeptides similar to EIA-1 antigens, and the other a neutralisation EIA (EIA-2N) based on antigenic competition with HCV peptides similar to EIA-2 antigens. The three samples not reactive in supplemental tests exhibited low EIA optical density (OD) values (signal/cutoff ratios of less than 3). Hence, all specimens reactive and yielding high OD values in both EIAs were also reactive in supplemental assays. Twenty four samples were reactive in EIA-1 only and nine (38%) of these were reactive in RIBA. Fourteen of the 15 (93%) specimens reactive in EIA-1 but not RIBA were derived from patients with chronic liver dysfunction. Two samples were reactive in EIA-2 only, of which one was reactive in EIA-2N and none in RIBA. CONCLUSIONS: Compared with EIA-2, EIA-1 yielded more validated reactive samples and resulted in more non-validated reactivities. It is therefore suggested that for clinical diagnosis: (i) EIA-1 be used for anti-HCV testing and EIA-2 for validation of EIA-1 reactivities; (ii) samples concordantly reactive in EIA-1 and EIA-2 and displaying high OD readings be considered HCV antibody positive without supplemental testing; (iii) supplemental testing by RIBA be limited to samples reactive in EIA-1 but equivocal or unreactive in EIA-2 and those concordantly reactive but exhibiting low absorbance readings.

Hemophilia A↗
PubMed1992

Human B19 parvovirus infection: an example of multiple pathogenic effects determined by differences in host susceptibility.

B19 infection offers some general lessons about human viruses and their possible effects on the human host, as follows: (1) Ubiquitous apparently benign viruses may have severe effects on a compromised host. The virus may be invariable but the host can have diverse susceptibilities. (2) B19 and some other human viruses (though for none is the evidence so clear as for B19) have narrowly targetted effects. The host cell of B19 is a specialised progenitor of mature red cells: impairment of the function of this cell by B19 may cause profound anaemia. (3) The 'normal' host response to B19 may also cause disease, though this is self limiting. (4) The effects of malfunction of the virus' target cell are exacerbated when the immune response is impaired by congenital or acquired immunodeficiency, immunosuppressive therapy or, in the case of the fetus, developmental immaturity that allows the virus to persist.

Adult↗
PubMed1992

Detection of HIV-1 antibodies in blood specimens spotted on filter-paper.

Described are the results of an international collaborative study to evaluate the use of whole blood samples spotted on filter-paper (BSP) for the detection of antibodies to human immunodeficiency virus type 1 (HIV-1). BSP samples were collected from 40 patients at risk for HIV-1 infection and tested blindly using commercially available HIV antibody test kits, either specifically manufactured or modified for this purpose. Parallel serum samples were also collected, and the antibody reactivity was defined and confirmed by Western blot. The results demonstrate that recovery of antibodies from BSP samples after elution can be comparable to that from serum. Some kits can be easily adapted to test BSP samples, while others cannot. At present, detection of HIV antibodies in BSP samples should therefore be carried out using kits specifically manufactured for this purpose or by the development of a modified protocol using a panel of BSP and their corresponding serum specimens.

AIDS Serodiagnosis↗
PubMed1991

HIV-2 in the United Kingdom--a review.

Human immunodeficiency virus type 2 (HIV-2) was first recognised in 1986 and subsequently the infection was shown to be widespread in West Africa. There have been few case reports from countries outside the African continent. In North America and Europe the highest number of infections have been in Portugal and France. Twelve HIV-2 infections have been identified in the United Kingdom (UK) and nine of the twelve had some connection with Africa, mostly West Africa; in three cases only "sub-Saharan Africa" was stated on the report, and one was from Mozambique. The other three HIV-2 infections were identified as follows: one in stored sera from a man who died in 1978, one in a child from Portugal who was diagnosed in the UK as having Acquired Immune Deficiency Syndrome (AIDS) in 1985, and one in a homosexual man who was tested unlinked and anonymously in London in 1987. It is not known how many of the total number of UK HIV-2 infections are represented by these twelve, but among large numbers of blood donors and people attending genitourinary medicine clinics the occurrence of infection was rare.

AIDS Serodiagnosis↗