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Biomedical subjects

T G Merrett

Publications and source records attributed to T G Merrett.

At least 37 records · Page 2Linked to original sources
PubMed1987

Phadiatop--a novel IgE antibody screening test.

The Phadiatop test, which is based on a multi-allergen allergosorbent, proved to be a test that is simple to perform in the laboratory and produces reliable results. When compared with the more conventional RAST atopy screening test for grass, mite and IgE antibodies it produced similar results, except in those rare instances of patients who were RAST-positive only for moulds where the Phadiatop test was decidedly superior. The Phadiatop test disc contains only inhalant allergens and so it could not be used for screening infants and very young children whose IgE response, if any, is probably limited to foods.

Evaluation Studies as Topic↗
PubMed1986

IgE antibodies to foods are not a feature of cystic fibrosis.

It has been suggested that patients with cystic fibrosis have abnormal immune responses to foods. We have measured IgE antibodies to inhalants and foods (by RAST) in 105 patients with cystic fibrosis aged between 8 months and 28 years. Serum IgE was elevated (greater than 180 kU/l) in 21 patients. In 43, IgE antibodies were detected in serum. The majority of positive results were with house-dust mite, grass pollen or Aspergillus. Only four of the patients had a positive RAST to a food--one to milk, one to wheat and two to egg. On the basis of high serum IgE or positive RAST results, 44.8 per cent of the patients were atopic and the frequency of atopy was age-related, being higher in patients aged 4 years or more. However, the presence of food antibodies was unrelated to age. This study confirms the high prevalence of atopy in patients with cystic fibrosis but unequivocally demonstrates that the presence of IgE antibodies to foods in their serum is rare.

Adolescent↗
PubMed1985

Food-allergic asthma in general practice.

A survey was undertaken to assess the importance of food allergy in asthma. Seventy-two asthmatics aged 15-60 years were identified in a general practice and compared with 72 controls matched for age and sex. A diagnostic procedure involving dietary elimination and challenge was carried out on those who thought food exacerbated their symptoms, together with those with concurrent eczema, positive skin tests to food or positive food IgE-RAST. The asthmatics more frequently had positive skin tests of IgE-RAST to food than the controls, but these tests proved to be rather non-specific in identifying provoking foods. One patient was found to be allergic to wheat and his clinical condition improved when wheat was removed from his diet. Two patients seemed to respond to other foodstuffs, but the effects were small, the foods (honey and peppermint) unimportant, and the patients' symptoms appeared to be largely due to other factors. Most cases of alleged food-induced asthma could not be confirmed by challenge testing. This survey suggests that some degree of provocation by food (excluding drink) affects at least 4 per cent of adult asthmatics, although in some of these patients it plays an unimportant part in the disease.

Adolescent↗
PubMed1984

Immunologic studies in allergen-induced late-phase asthmatic reactions.

We have measured plasma histamine, serum neutrophil chemotactic activity (NCA) and complement (C3 and C4) over a 24-hour period in patients experiencing either early- and late-phase (dual) or single early asthmatic reactions to inhaled allergens. There was a significant biphasic elevation in plasma histamine, which paralleled the fall in forced expiratory volume in 1 sec in 10 patients with dual responses, whereas in seven subjects with single early reactions, only a single early increase in histamine concentrations was observed. In general, in the individual subjects, the changes in plasma histamine paralleled both the elevations in serum NCA and the decreases in forced expiratory volume in 1 sec. By gel filtration on Sephacryl S-400, anion exchange chromatography on DEAE Sephacel, and chromatofocusing with Polybuffer Exchanger 94, the major NCA of both the early and the late reactions was associated with proteins having an estimated molecular size of 600,000 daltons, an elution from DEAE Sephacel at 0.15M to 0.30M of NaCl (pH 8.1), and a pI of approximately 6.5. There were no appreciable changes in serum C3 and C4 up to 24 hr after challenge in subjects with late-phase responses. The patterns of asthmatic response were not related to either the total or allergen-specific serum IgE or IgG4 concentrations. These results support the view that mediators of hypersensitivity participate in late-phase as well as early asthmatic reactions.

Adolescent↗
PubMed1984

Immediate hypersensitivity, IgE and asthma.

Twenty-one asthmatic and twenty-two non-asthmatic children and nine asthmatic adults from two different rural areas of Tanzania, and eight asthmatic children from Dar-es-Salaam were surveyed by questionnaires, skin testing and the measurement of serum IgE. Asthma was significantly commoner in female rural children (four males, fifteen females). The rural asthmatic children apparently had less skin reactivity (in seven of nine tests) and lower specific (in two of four tests) and total serum IgE than age-, sex- and village-matched controls. This pattern of asthma in rural children in the tropics represents a different type of asthma from that found in temperate zones. In contrast, the adult rural asthmatics and the urban children seemed to have the pattern of increased skin reactivity and serum IgE found in asthmatic patients from temperate climates.

Asthma↗
PubMed1984

Total and specific IgG4 antibody levels in atopic eczema.

Total IgG4 and IgG4 antibody levels specific for 10 allergens (three inhaled and seven ingested) were measured by radioimmunoassay of sera taken from three groups of adult patients: (1) 32 cases of atopic eczema, (2) 28 cases of respiratory allergy and (3) 156 normal volunteers. In all three groups IgG4 antibody activity was mainly directed against common foods, and generally the group with atopic eczema had higher total and specific IgG4 levels than the cases of respiratory allergy, who in turn had higher titres than the normal group. There was within each group a tendency for men to have more total IgG4 than women and the difference was statistically significant among the normals. There was evidence of an IgG4 restricted response in atopic eczema because despite the group's elevated total IgG4 its total IgG4 remained within normal limits. Furthermore specific IgG4 was correlated with the corresponding specific IgE level in five of the 10 allergens examined. These results are generally consistent with the view that IgG4 levels are raised in cases of atopic eczema due to prolonged exposure to an allergen which initiated an IgE response.

Adolescent↗
PubMed1983

Food intolerance: a community survey.

1. A questionnaire inquiring about food intolerance was sent to a random sample of the electorate in a small South Wales town. Replies were received from 170 men and 305 women, the response rates being 87 and 93% respectively. 2. Adverse effects of some food were reported by 19% of men and 26% of women, or 14 and 18% respectively if minor digestive symptoms are excluded. Certain foods were thought to cause non-abdominal symptoms by 4% of men and 10% of women, and vomiting, diarrhoea or abdominal pain by 11% of men and 10% of women. 3. Plasma IgE was measured in a random subset of ninety-nine women and found to be significantly lower in those with major symptoms than in the rest. This suggests that allergy is probably not a common cause of food intolerance.

Female↗
PubMed1983

A community survey of IgG4 antibody levels.

Precise and specific radioimmunoassays have been developed to quantify IgG4 and IgG4 antibodies. A community survey has demonstrated that men have significantly higher total serum IgG4 levels than women: geometric mean values of 0.581 mg/ml versus 0.302 mg/ml. This sex difference was extended to total IgE values. Circulating levels of IgG4 antibodies against foods, especially egg and milk, were normally higher than those against the three most common U.K. inhalant allergens--grass pollen, house dust mite and cat epithelium.

Adolescent↗
PubMed1983

Food related antibodies in headache patients.

Highly sensitive and specific methods for assaying IgE and IgG4 for antibodies in serum have been developed in order to test a recent suggestion that food allergy is a major cause of migraine. Sera were collected from 208 adults--74 with dietary migraine, 45 with non-dietary migraine, 29 with cluster headache and 60 controls. No significant differences were identified between any of the groups with the one exception that cluster headache patients had significantly raised levels of total serum IgE: this difference may be explained by the high proportion of smokers. Mean IgG4 titres to cheese, milk and chocolate were very similar in the dietary and non-dietary migraine patients and the control subjects, though lower in the cluster headache patients. There was, therefore, no evidence that the food intolerance often associated with migraine headaches is associated with a conventional allergic mechanism.

Cluster Headache↗
PubMed1982

Allergy screening using a microcomputer.

Data are presented to show that a microcomputer can be programmed to: (1) analyse a standard allergy questionnaire, (2) reliably predict the ranked order probabilities with which IgE antibody tests will produce positive results, (3) store the IgE test results, and (4) print a comprehensive report that summarises and integrates the clinical and laboratory data. Consequently, the practitioner who refers a blood sample and a questionnaire completed by the patient to a centre where both can be analysed will obtain enough practical information to decide whether to treat or refer that patient to a specialist. The microcomputer is therefore potentially of great value in any preliminary allergy investigation.

Computers↗
PubMed1982

Comparison of reverse passive antiglobulin haemagglutination with double antibody radioimmunoassay for estimation of total human serum IgE.

Serum IgE levels can be measured by reverse passive antiglobulin haemagglutination (RPAH) using trypsin-treated human red cells coupled to anti-human IgE by chronic chloride. The results are read after only 90 min incubation. RPAH and double antibody radioimmunoassay have been used to measure IgE levels in 100 sera, with levels ranging from 5 to 43,000 international units (i.u.)/ml. Correlation between the two assays was high over the whole range, provided that affinity-purified anti-IgE was used in the RPAH test. When two non-affinity-purified anti-IgE reagents were used in the RPAH, correlation was poor for sera with levels below 1000 i.u./ml. It is concluded that RPAH tests for IgE are of comparable sensitivity and specificity to radioimmunoassay procedures, and provide a useful simple, yet more rapid alternative.

Antibodies, Anti-Idiotypic↗