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Biomedical subjects

T G Merrett

Publications and source records attributed to T G Merrett.

At least 55 records · Page 3Linked to original sources
PubMed1981

An automated particle-counting immunoassay (PACIA) for serum IgE.

Total IgE was determined in 107 sera using a novel, automated, non-isotopic immunoassay called PACIA (particle-counting immunoassay) based on agglutination of anti-IgE coated latex particles by IgE. The IgE values ranged from 10 to 50,000 iu/ml and were compared with results obtained by a conventional radioimmunoassay (RIA) which used a fast double antibody separation technique--the coefficient of correlation was 0.985 and the regression line y = 0.82 x +130.00. PACIA had several advantages over the RIA technique: using a sampling rate of 50/hr, results were obtained in 35 min compared to 16-20 hr, no labelled IgE was required and the separation step, which relied on measuring the number of non-agglutinated particles by an optical cell counter, was fully automated. The threshold of sensitivity was 10 iu/ml and the maximal coefficient of variation for between assay precision was 12.9%.

Humans↗
PubMed1981

Studies on hyperimmunoglobulinaemia E in atopic diseases with particular reference to food allergens.

Total and specific IgE have been measured in serum, suction blister fluid and jejunal aspirate in patients with various atopic disorders in an attempt to increase our knowledge of the association between food allergy and adult atopic eczema. We found (a) that patients with atopic disorders, irrespective of whether the disease affects primarily the skin or airways, have raised IgE concentrations that are largely attributable to antibodies directed against inhaled allergens; (b) that IgE antibodies against food allergens account for an appreciable amount of the total IgE in patients with atopic eczema though not as much as that contributed by inhalants; and (c) that in patients with atopic eczema, most of the IgE is produced at sites other than the intestine or skin.

Adolescent↗
PubMed1980

Assessing the value of skin prick tests.

Skin test materials vary in their potency and specificity. Although 3 mm reactions are often regarded as diagnostic of a type 1 allergy, a study based on 100 allergy clinic patients with food intolerance showed that thirteen out of fifteen patients with a 3 mm reaction to common inhalant allergens had no RAST-detectable allergen-specific IgE. Three millimetre reactions were significant for milk and egg extracts. Food intolerance was clinically demonstrable in six out of seven patients giving a 4 mm skin reaction and in ten out of thirteen with a 3 mm reaction. There was, however, a "clinically false positive" reaction of 3 mm or more in 3.8% of allergy clinic patients for milk and 2.8% for egg. In fifteen out of nineteen patients with a clinical diagnosis of fish allergy, the diagnosis was supported by a skin test reaction of 5 mm or more. However, seven patients with no history of intolerance to fish gave a 4 mm reaction to the same extract. Reactions of less than 5 mm were thus unhelpful clinically.

Animals↗
PubMed1980

Circulating IgE levels in the over-seventies.

In a normal population aged over 70 years the geometric mean IgE value of 30.6 u/ml was not significantly different from that obtained previously in a similar epidemiological survey of a population aged 20-44 years. However, in the older population we have noted a significant sex difference-38.6 u/ml for males against 27.2 u/ml for females-which was only apparent in the atopic subjects of the younger population. There have been some other reports that IgE levels decrease with age, and possible reasons for these differences with our own results are discussed.

Adult↗
PubMed1980

Screening for IgE-mediated allergy.

Sera from 425 patients were analysed with Phadebas RAST reagents against a panel of 19 allergens and the most commonly positive results were to grass pollen, Dermatophagoides pteronyssinus and cat epithelium. Of the 275 sera RAST-positive to any allergen, 261 were positive by a RAST technique which used a mixture of the three most common U.K. allergens; the remainder were usually positive to a mould. We conclude that 1) when a positive result is obtained after screening by the mixed-allergen RAST and a representative mould RAST, then other positive RAST results are possible, but that the extent of the investigation can be guided by a knowledge of the total serum IgE level and a computer-based history analysis; 2) when a mixed-allergen RAST and a representative mould RAST is negative, then a more specified RAST including all 19 allergens used in this investigation will be negative; 3) a positive mixed-allergen RAST result is likely to be associated with a total serum IgE level over 40 U/ml and a positive symptom pattern score derived from the computer-based history analysis.

Adolescent↗
PubMed1980

Effects of anti-mite measures on children with mite-sensitive asthma: a controlled trial.

Mite counts and tests for mite antigen were performed on samples of dust taken from the bedding of 53 children with mite-sensitive asthma. The samples from damp houses and the beds or enuretic children had markedly more mites and mite-antigen than those from dry houses. although the predominant species was usually Dermatophagoides pteronyssinus, some of the beds in the damp houses were heavily infested with another pyroglyphid mite Euroglyphus maynei, so that this was the species found in the greatest numbers. D pteronyssinus antigen was found to be correlated broadly with the total mite count, but more antigen was present for a given number of mites in the mattresses than in the blankets. The children were randomly allocated into two groups, one of which carried out rigorous anti-mite measures. The amounts of dust and mite antigen were reduced, though not the numbers of mites. Peak flow readings were monitored in the two groups for eight weeks and a final assessment made by a paediatrician who was unaware of the allocation of each patient in the trial. No significant differences emerged in the progress of the two groups, both tending to improve. Measures designed to remove mites from bedding do not greatly benefit the majority of children with mite-sensitive asthma.

Adolescent↗
PubMed1980

Food allergy and intolerance in 100 patients---local and systemic effects.

One hundred patients who reacted adversely to one or more specific foods were studied. In 93 the food induced symptoms included asthma, eczema, angioedema, urticaria, rhinorrhoea, or a combination of one or more of these with gastrointestinal symptoms. The remaining seven had gastrointestinal symptoms only. The diagnosis of food allergy was made on the on the basis of a definite, immediate allergic reaction to specific foods or a reaction that was suggestive of allergy, supported by a corresponding positive skin prick or radioallergosorbent test. In the absence of such evidence, the less specific diagnosis of 'food intolerance' seemed preferable. Test materials appeared to differ in their diagnostic usefulness. A high proportion (c. 75 per cent) of patients who were intolerant to egg, fish or nuts had positive test results. In contrast, only 30 per cent of patients with milk intolerance had positive tests, suggesting inadequate test methods or a non-allergic cause for many patients' milk intolerance. Nevertheless, five milk intolerant patients with negative tests had milk-induced asthma.

Adolescent↗
PubMed1979

The radioallergosorbent test (RAST) in nasal polyposis.

The incidence of atopy among 64 adults undergoing polypectomy was 25 per cent. Among these atopic patients it was usual for the polyp IgE level to exceed that in the serum. Similarly, D. pteronyssinus-specific IgE was more commonly identified in polyp fluid by the RAST technique than in serum. However, this was not so for grass pollen-specific IgE, where serum and polyp fluid were equally positive. We conclude that there are atopic and non-atopic polyps.

Adult↗
PubMed1979

Epithelial or dandruff allergen for the diagnosis of dog allergy by RAST?

When used for screening by the RAST technique, dog epithelium provided too few positive results (29.2%) compared with dog dandruff (58.8%), cat epithelium (53.6%) and horse dandruff (52.2%). However, dog dandruff can provide an unexpectedly high incidence of positive RAST results (45.2%) in sera from patients with an allergic history to cat or horse, but not to dog. Dog dandruff allergens were found to cross-react with some cat or horse serum proteins in about 25% of such patients. We conclude that dog dandruff is preferable to epithelium for screening by the RAST technique, but if emotional issues involving a family pet arise then confirmation by a trial separation is likely to be more convincing than a provocation test with a possibly non-specific allergenic extract.

Allergens↗
PubMed1978

Methods of quantifying circulating IgE.

Four radioimmunoassay techniques, two conventional and two sandwich, have been used to measure circulating IgE levels in 100 sera. The test sera had IgE levels ranging from 1.0 to 20,000 u/ml, and each was measured at five dilutions, ranging from three-fold to 400-fold. The same IgE standards were used throughout, and the optimal range for each assay was determined by assessing data for quality control sera and the WHO standard 69/204. To be of general use in the United Kingdom an IgE test must measure accurately levels as low as 20-30 u IgE/ml. The Phadebas RIST method failed to meet this criterion, and of the remaining tests the double antibody method had the most useful operating range and produced the most reliable results. However, the double antibody method is not available commercially and so, for the majority of laboratories, the Phadebas PRIST technique should be the method chosen.

Animals↗
PubMed1978

Computer analysis of allergic histories taken by questionnaire.

We report the development of a detailed allergy questionnaire designed so that the answers can be typed into a mini-computer. Computer programmes have been written to file and to retrieve these answers, and to print a summary which is then 'weighed', so as to produce a clinical atopy score which is then further broken down into indoor and outdoor scores. In a pilot survey of ninety patients, their clinical atopy scores and immunoglobulin E (IgE) profiles have been compared, and additional computer programmes have been written which will (a) assess if a more detailed IgE investigations is warranted, and (b) suggest which allergens, if any, are likely to be responsible for the patients' symptoms.

Adult↗
PubMed1978

RAST atopy screen.

A single in vitro screening test for atopic allergy is described. It uses the radioallergosorbent test (RAST) principle, and has been applied to screening sera from U.K. patients with possible atopic symptoms. When compared with the Phadebas RAST, the test sensitivity was 97% and the specificity 100%, and these results suggest that it is useful in any preliminary allergy investigation.

Animals↗
PubMed1977

Prognostic value of serum levels of immunoglobulins (IgG, IgA, IgM and IgE) in breast cancer: a preliminary study.

One hundred and sixty women admitted for breast tumour biopsy to the King's College Hospital group have been followed sequentially for 2 years. Sixty-nine women had early operable breast cancer and 91 had benign breast disease. All these women had serum immunoglobulin IgG, IgA, IgM and IgE levels measured preoperatively and postoperatively at 3 months, 1 year and 2 years. No differences were found in any of the serum immunoglobulin levels between the two groups at any time. There was, however, a positive correlation between the extent of metastatic breast cancer and the serum level of various immunoglobulins, particularly IgA. There was no evidence that routine postoperative radiotherapy influenced the levels of serum immunoglobulins. The findings suggest a secondary defence reaction against increasing tumour load, and do not support the theory of an early immune defect in immunoglobulin metabolism which could play a part in the pathogenesis of breast cancer. Although there is no diagnostic value in measuring the levels of serum immunoglobulins in patients with breast tumours, there may be some value in following the levels in cancer patients, as a guide to subclinical spread of the disease.

Aged↗
PubMed1977

IgE, parasites and asthma in Tanzanian children.

Two rural Tanzanian primary schools were surveyed to test the hypothesis that parasitic infestation prevents the development of asthma. 242 pupils were interviewed to determine the prevalence of pupils with recurrent episodes of wheezing. The nineteen pupils so discovered had more exercise-induced bronchial lability than equivalently exercised controls. More girls (12.8%) than boys (3.3%) had asthma. In one school, 77% of the controls had faecal parasites, mainly Ascaris spp., and in the other school 55% of the controls had Schistosoma haematobium in their urine. Parasites were found in similar proportions in the asthmatics. The mean serum IgE for the whole population was 3174 u/ml with no demonstrable difference between the asthmatics and controls. There was no difference in immediate cutaneous hypersensitivity to twenty-two allergens between the asthmatics and controls. These findings suggest that parasitic infestation does not prevent the development of asthma.

Adolescent↗