Comparison of a multi-allergen dipstick IgE assay to skin-prick test and RAST

A multi-allergen dipstick enzyme immunoassay 'Quidel Allergy Screen' (QAS) has recently been developed commercially for measuring IgE antibodies against nine allergens (house dust 1, house dust 2, Dermatophagoides pteronyssinus, D. farinae, Japanese cedar, ragweed, cat dander, sweet vernal grass, and egg white) at one time. To assess whether this assay is useful in screening allergen-specific IgE antibody, we compared the titres of IgE antibodies against the nine allergens measured by QAS to those in the skin-prick test and by RAST in 93 atopic asthmatics and 22 normal subjects. We found a good overall agreement between the results of the skin-prick test and the results of QAS (sensitivity = 47.1-81.4%, specificity = 84.5-100%, and agreement = 78.9-88.9%). The sensitivities against house dust 1, D. pteronyssinus, and D. farinae ranged from 77.2 to 81.4%. However, the sensitivities against house dust 2, Japanese cedar, ragweed, and cat dander were low (47.1-68.8%). We also found a good overall agreement between the results of RAST and the results of QAS, except for egg white (sensitivity = 46.2-94.4%, specificity = 87.4-100%, and agreement = 77.4-96.5%). The sensitivities against house dust 1 and 2, D. pteronyssinus, D. farinae, and Japanese cedar ranged from 86.0 to 94.4%. The sensitivities against ragweed, cat dander, and sweet vernal grass were low (46.2-52.6%). There were strong correlations between the titres of RAST and the titres of QAS except cat dander and egg white (r = 0.701-0.924 for the seven allergens). Thus, we conclude that QAS is useful in screening IgE antibodies against multiple allergens at one time. However, because the sensitivities against some allergens tested were low, further improvement of some allergen preparations seems to be necessary in the assay.     

Environmental and Social Influences on Skin Test Results in Children

Skin tests with 13 inhalant allergens were performed in 788 children with respiratory allergy. Positive reactions were common to animal danders (65%), to grass pollens (55%) and to tree pollens (44%) but rare to moulds (13%) and to house dust mite (12%). Children exposed to cows, dogs or horses at home more often had skin test reactions to these allergens than the children not exposed, but reactions to cat dander occurred as frequently in children exposed to cats at home as to those not exposed. Reactions to three pollens occurred most often in children from upper social classes and from urban areas and reactions to house dust mite occurred most often in children from lower social classes and from rural areas. Children with positive reactions to house dust mite came from larger families than children with negative test results.     

Predictivity of allergic sensitization (RAST) for the onset of allergic diseases in adults

Background:  Specific IgE antibodies are often detected without any clinical manifestation of allergies. We aimed to analyse the predictivity of allergic sensitization for incident symptoms of allergic diseases in adults during a 10-year follow-up .
Methods:  In 1994/95 specific IgE antibodies against five common inhalant allergens (grass pollen, birch pollen, house dust mite, cat dander and Cladosporium ) were diagnosed by radioallergosorbent test in 4178 adults aged 25–74 years. A subset of 2656 participants could be re-evaluated in 2004/05. Information on socio-economic factors and medical history, including data on atopic diseases, was assessed by a combination of a personal interview and a self-administered questionnaire. Logistic regression models were applied to study associations between allergic sensitization and incident allergic diseases.
Results:  Allergic sensitization was an important predictor for incident hay fever (OR 7.95, CI 95% 4.64–13.62) and asthma (OR 1.82, CI 95% 1.29–2.57). Specific IgE antibodies were mainly related to outdoor allergens (grass and birch pollen) for hay fever and indoor allergens (mite and cat dander) for asthma, while for atopic dermatitis no specific IgE antibodies were identified as major predictors.
Conclusions:  Allergic sensitization not only covers clinically apparent allergies, but indicates a prognostic factor for later allergies, even in adulthood.     

Skin tests and blood leukocyte histamine release of patients with allergies to laboratory animals

Skin tests and in vitro histamine-release reactions were used to evaluate 130 patients observed in an employee allergy clinic at a biomedical research facility. The allergens used included extracts from pollens (ragweed, grasses, trees, weeds), molds, mixed feathers, house dust, cat, dog, mouse, rat, rabbit, guinea pig, and hamster. Of all patients, 66% complained of allergic symptoms on laboratory animal exposure, although only 52% worked directly with animals. Among patients with symptoms, 91% were positive by skin test to at least one laboratory animal, and 46% had asthma. The median length of exposure to laboratory animals before onset of symptoms was 2.8 yr with 60% of the patients developing their symptoms within 3 yr. Among patients who had allergic symptoms before exposure to laboratory animals, 79% were skin test positive to laboratory animals when they were evaluated in this study. There was a close association found between the skin test and histamine-release results with the laboratory animal allergens: 91% of the 4+ skin reactors had leukocytes positive for histamine release versus 5% of the leukocyte donors with less than 1+ skin reactions. A close relationship in positive reactions to different laboratory animal allergens was also found. For example, individuals positive to mouse were positive also to rat (95%), rabbit (79%), guinea pig (83%), and hamster (88%). Patients who reacted to laboratory animals also reacted to some extent to house dust and cat and dog allergens, and about one half of the animal-allergic individuals reacted to pollens. Although nonpollen-allergic individuals can develop sensitivity to laboratory animals, the group at higher risk are allergic individuals, especially those sensitive to house dust, cats, or dogs.     

Animal danders

Animals release proteins into their surroundings through secretions, as excretions, or as dander. The quantity of dander that is dispersed by cats, dogs, or humans is sufficient to supply food for dust mites and to supply easily measurable quantities of proteins in dust. Fel d 1, Can f 1, and human IgA or IgG can be found in microgram quantities in dust samples. Allergens also can accumulate from the urine of wild or pet rodents. For cats and dogs, the accumulation of dander particles is not related to the cleanliness of the animals. All animals, including humans, provide a fully adequate supply of organic material for bacterial growth in a carpet, provided conditions are sufficiently humid. The authors' preliminary results in Virginia do not find a significant difference in endotoxin between homes with or without animals. The likely explanation for the nonallergic IgG and IgG4 response to cat, dog, or rat allergens is high exposure to proteins from these animals. If the highest levels of cat allergen in a home can result in immunologic tolerance, it is unlikely that primary avoidance would be successful at reducing exposure. The data showing that 80% of Swedish children with cat allergies never had lived with a cat imply that the concentrations of cat allergen in schools or in houses without a cat are sufficient to cause sensitization. Primary prevention would be possible only on a community basis, which is unlikely to occur. Sensitization to cat, rat, dog, or mouse allergens consistently is associated with asthma. In symptomatic children with positive skin test results, there is a strong case for allergen avoidance and a clear need for controlled trials. Controlled trials of avoidance should include houses without cats and schools. Controlling exposure to cat allergens with the cat in situ requires aggressive measures, such as removing reservoirs, washing the cat, and air cleaning. Many allergic or symptomatic children who live with a cat do not have positive skin test results or positive IgE antibodies to cats. Avoidance measures related to animals should be recommended only for individuals with positive skin test results. Increasing evidence shows that exposure to cats, dogs, rats, and other animals can induce a form of immunologic tolerance without causing allergic disease, and it is important to understand why this change occurs with dander allergens rather than with all allergens. The most probable explanations are related to the form and quantity of airborne allergens.     

Clinical associations with serum allergen-specific IgG4 antibodies

Serum total and allergen-specific IgE and IgG4 antibodies, were measured in eighty-seven atopic and nineteen non-atopic asthmatics. The allergens studied were: Dermatophagoides pteronyssinus, grass pollens, cat dander, dog dander, milk and egg. Sixty-eight atopic asthmatics and fourteen non-atopic asthmatics were found to have allergen-specific IgG4 antibodies, to at least one of the allergens tested. IgG4 antibodies to milk and egg were common in both groups of asthmatics, and to animal danders in the non-atopic asthmatics. Skin prick tests were always negative when allergen-specific IgG4 antibodies occurred alone, but in such cases, intradermal skin tests were positive. Seventy-five per cent ofa group of patients with normal levels of serum total IgG4, were found to have at least one positive IgG4 RAST.     

The relative risks of sensitivity to grass pollen, house dust mite and cat dander in the development of childhood asthma

The associations between skin sensitivity to various common allergens and the development of childhood asthma were ascertained in a longitudinal study of a birth cohort of New Zealand children up to the age of 13 years. Of 714 children skin-tested, 45.8% were sensitive to at least one of 11 allergens, the most common responses being to rye grass pollen (32.5%), house dust mite (30.1%) and cat dander (13.3%). Allergen-specific relative risk analysis, controlled for the effect of sensitivity to other allergens, demonstrated that sensitivity to house dust mite and to cat dander were highly significant independent risk factors associated with the development of asthma (whether defined as recurrent typical respiratory symptoms, increased airway responsiveness, or the concurrent presence of both), whereas grass sensitivity was not a significant independent risk factor for asthma.     

Animal dander allergy

In a group of twenty-three atopic patients skin tests were performed with the dander allergens of horse, cat and guinea-pig, and with house dust and Timothy pollen allergens. A good agreement was observed between positive skin reactions and the results of RAST with these various allergens. In a number of cases, positive skin reactions were not related to the clinical histories. Likewise, positive RAST scores in several instances proved clinically meaningless. In patients with history-related skin reactions better correlation with RAST was observed. In such patients, skin reactions with photo-inactivated allergens remained strongly positive.     

Inhibition Experiments with Solid Phase Mite or Epithelia in House Dust Hypersensitivity

The present study was undertaken to verify that mites are not the only allergens in house dust extracts and that other allergens such as cat epithelia can also be responsible for house dust hypersensitivities detected both by house dust skin tests and house dust RAST studies. In order to determine whether mite or epithelia fixed on a solid phase could remove not only the IgE antibodies reactive with the homologous allergens, but also the IgE antibodies reactive with house dust allergens, the authors have absorbed 10 sera of house dust allergic patients with solid phase mite or epithelia. The absorption procedure removed a large part of the IgE antibodies reactive with specific immunosorbent (Dermatophagoides pteronyssinus or cat epithelia) and in the same way the IgE antibodies reactive with house dust immunosorbent. The percentage of RAST inhibition varied from 65% to 92% for Dermatophagoides pteronyssinus and from 65% to 94% for house dust in patients allergic to house dust and mite; the percentage of RAST inhibition varied from 67% to 92% for cat epithelia and from 73% to 90% for house dust in patients allergic to house dust and cat epithelia. This is in accordance with the hypothesis that house dust is not an allergen per se, but rather a complex mosaic of several allergens including mite, animal epithelia, etc.     

Human dander in house dust allergy

The possible role of human dander in house dust allergy was investigated. Naturally shed human mite-free skin squames were collected from bedding and used to prepare a human dander extract. When the extract was coupled to cyanogen bromide-activated paper discs, and used in the RAST assay, IgE titres to the skin extract were observed in the sera from several patients with house dust allergy. The sera with IgE to the skin extract also had high IgE titres to either house dust, D. pteronyssinus or cat fur. RAST inhibition studies revealed cross-reaction between the human skin extract and both a D. pteronyssinus extract and a cat fur extract.     

Histamine-Dependent Allergy Blood Test

Allergen-mediated histamine release from human leukocytes represents an important model for in vitro studies of allergic reactions. The purpose of this study was to determine whether the measurement of histamine released in allergic patients by radioenzymatic assay following mixing of their blood with common allergens represents a reliable index for diagnosis of atopic allergy. Three categories of allergens were used: 1) house dust and mite; 2) cat and dog dander; 3) trees, grasses and ragweed mixture. The presence of allergy was established by clinical history and intradermal skin testing in the study group of 150 patients. A significant allergen-mediated histamine release ranging from 4 to 65% of the total blood histamine content was observed in 96% of the patients with skin test sensitivity of greater than or equal to 3+. There was a significant correlation between skin testing and histamine release in terms of the allergens causing the response. Thus, the measurement of histamine by radioenzymatic technique following its release in blood in response to allergen challenge represents a clinically useful in vitro test for the diagnosis of atopic disease.     

Discrepancies between the skin test and IgE antibody assays: study of histamine release, complement activation in vitro, and occurrence of allergen-specific IgG

Intracutaneous skin tests (STs) and RAST with the common allergens, grass pollen, house dust mite, and cat dander, were performed on 660 adult patients. In 117 patients (18%), we found 140 discordances (7%) in a total number of 1980 ST and RAST combinations. In agreement with studies in the literature, greater than 80% of the discordances consisted of positive skin reactions without detectable allergen-specific IgE antibodies in serum. The percentages of discordant results were similar for the three allergens. Reproducibility of both the RAST and the ST was evaluated in the discordant group. Repetition of the routine RAST procedure elicited results similar to those in the first test in 81% (105/130). A second ST elicited identical results in 89% (47/53). In addition to the routine IgE antibody assay, sera of patients with a positive ST but without detectable IgE antibodies were tested in two other RAST systems: (1) a RAST with allergen extracts from the same production batch as the ST reagents, and (2) the Pharmacia RAST. In spite of having a clearly positive ST, sera from 68 (80%) of 85 patients remained completely negative in all three RAST systems. Histamine release (HR) in vitro from washed leukocytes was studied in 35 patients with a reproducible positive ST and negative RAST results with serum. Interpretation of this test was possible in 28 patients. In 82% (23/28) of these patients, clearly detectable HR was found with the relevant allergen extract. A role of IgE in the skin reactions and HR tests was confirmed by positive RAST results with IgE that was affinity purified from serum of seven of these patients. Allergen-specific IgG4 antibodies are unlikely to be implicated, since no antibodies against grass pollen and house dust mite were detectable in sera of these patients. Only 18% of the patients with an unexplained skin reaction with cat dander have detectable IgG4 antibodies, but these antibodies were found in a similar frequency in a nonallergic, ST negative control group. Low total IgG responses precluded false negative RAST results caused by competition of IgG antibodies with IgE antibodies. There were no significant differences in the degree of complement activation in vitro by house-dust extracts between healthy control subjects, nonallergic patients, and patients with unexplained skin reactivity. It is concluded that a high proportion of the positive skin reactions with common inhalant allergens, which are not accompanied by a positive RAST, are probably caused by IgE antibodies that are not detectable in serum with any of the RAST procedures.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dust from carpeted and smooth floors. I. Comparative measurements of antigenic and allergenic proteins in dust vacuumed from carpeted and non-carpeted classrooms in Norwegian schools

Dust samples from fitted-carpets and linoleum floors in 12 schools in Norway were collected by vacuum cleaning. The presence of antigens and allergens of alder (Alnus incana), birch (Betula verrucosa), timothy (Phleum pratense), mould (Cladosporium herbarum), house dust mite (Dermatophagoides farinae), cat and dog dander, codfish, hen egg white and human dander were investigated by crossed immunoelectrophoresis (CIE), crossed radio-immunoelectrophoresis (CRIE) and radio-allergosorbent test (RAST) inhibition. No qualitative differences in allergen contents of dust from both types of floor tested were noted. Similarly, no relationship could be demonstrated between floor-type and allergen concentration under identical experimental conditions. Antigens and allergens of both cat and dog were frequently demonstrated in dust extracts. All extracts included human dander and mould allergens. In addition, most dust samples from both carpeted and smooth floors contained hen egg white and codfish allergens. Furthermore, the study demonstrated that dust from smooth floors and fitted-carpets was relatively free of mite and pollen from alder, birch and timothy.     

Positive skin tests to aero-allergens and month of birth

The month of birth distribution for 1301 French patients born between 1953 and 1975 with at least one positive skin test was compared to that of the whole population. A chisquare test was performed, and the expected birth month distribution of the groups calculated from the INSEE * data for 1953-1975. All patients underwent skin testing with house dust, Dermatophagoides pternyssinus (Dpt), cat and dog allergens, grass, tree and weed pollens, and moulds. The only study criterion was a positive skin test unrelated to any specific disorder. A significant difference in month of birth distribution was observed 1) for patients with positive skin test to grass pollen, with a high rate of births from January to May, and 2) for patients with mould sensitization, with a low rate of births in April, May and December. Tree and weed pollens, house dust and Dpt showed no significant relation with month of birth. For cat and dog allergens, the observed and expected distributions of birth month were similar. For the whole sensitized population the birth rate tended to be low in December except for the cat and dog sensitized. Our study confirms the well-known seasonal peak of births in the first 5 months of the year for grass pollen sensitized patients. No consistent monthly or seasonal tendency could be statistically demonstrated for other allergens except moulds.     

Relationship of Allergen-Specific IgE Antibodies, Skin Prick Tests and Allergic Disorders in Unselected Adolescents

The relationship between serum levels of allergen-specific IgE (RAST) and skin prick test reactivity and allergic disorders was evaluated in 137 subjects randomly selected from an adolescent population. All subjects were prick tested with six common allergens, interviewed and physically examined. In addition, serum was collected for RAST analysis with three to six allergens. At least one positive RAST result (score 1-4) was observed in 40% and at least two positive RASTs in 22% of the subjects. Boys experienced more RAST reactions and generally with higher scores than girls. For instance, 26% of boys but only 11% of girls were RAST positive to timothy grass pollen. The correlation between prick test and RAST results was better with pollens than with house dust and animal epithelia. When the test results were discordant, the skin test was usually positive and RAST negative. Many of the small skin reaction (weal diameter 3-4 mm) were accompanied by a negative RAST. Respiratory allergy was closely connected with both positive skin test and RAST reactivity, while atopic dermatitis was less related. In 17% of the adolescents positive skin tests and in 14% positive RASTs occurred in the absence of any allergic symptoms. We conclude that a positive RAST score 3-4 to inhaled allergens is a strong indicator of clinical allergy but low scores 1-2 are frequently found in healthy young people.     

Activation of the classical pathway of human complement in vitro by house-dust extracts is caused by IgM antibodies to polysaccharide antigen(s) and is not related to atopy

The mechanism of activation of the classical pathway of human complement by house-dust extracts and its relevance to atopic disease was studied. Our results confirm that for most sera of adults, house-dust extract is, on a weight basis, a more potent C-activator than aggregated human IgG or lipopolysaccharide (endotoxin). Naturally occurring IgM antibodies directed against ubiquitous polysaccharides appeared to be the dominant factor in the C1 activation by house-dust extracts in human sera. Large variations were found between sera with respect to the concns of these IgM antibodies as measured by C1 activation or fixation of haemolytic complement. The IgM antibody titre was, however, not associated with atopic disease. Consequently, we do not support the hypothesis put forward by Berrens et al. (1978) (Allergol. Immunopath. 6, 45-54) that there might be a relation between atopy and enhanced reactivity of serum complement with allergenic extracts. More than 90% of the C-activating potential of allergen extracts like house dust was found in the fractions with high mol. wt material (mol. wt greater than 100 K). Therefore, these antigens are easily separated from the known IgE-binding major allergens of house-dust mite and cat dander.     

Relationship between skin-prick tests, the multiple allergosorbent test and symptoms of allergic disease

In 47 atopic subjects, skin-prick testing to 10 common allergens was performed, and specific IgE to the same allergens was assessed by the multi-allergosorbent chemiluminescent assay (MAST-CLA). Overall agreement between the tests was 66.4% for conventionally positive skin tests (weal diameter greater than or equal to 3 mm), rising to 78.5% when a positive skin test was defined as having a weal diameter greater than or equal to 5 mm. Agreement between the tests was statistically significant for all allergens except Alternaria. A history was obtained from each subject of the presence or absence of allergic symptoms on exposure to cats, and whether there was a history of grass pollen allergy. MAST-CLA testing for specific IgE to cat dander predicted a history of cat allergy with an efficiency of 74.5%, while a positive MAST-CLA test for Cocksfoot grass predicted a history of grass pollen allergy with an efficiency of 85.1%. Similar results were obtained on skin testing for these allergens. We conclude that MAST-CLA gave results comparable to those obtained by skin-prick testing, and correlated equally well with the history of allergic symptoms.     

Inhalant allergy to wild animals (deer and elk)

We studied 15 highly atopic persons with historic and/or skin test evidence of allergy to deer or elk. All 15 were also reactive to domestic animal danders (dog, cat, or horse). Twelve patients had elevated IgE antibody levels to deer hair/dander and six patients had elevated IgE antibody levels to elk hair/dander. Elevated IgE antibody levels to serum or urine from deer or elk were found in six persons. By using individual patient sera in RAST inhibition experiments we showed that IgE antibodies were directed to allergens common to hair/dander, urine, and serum. One individual reacted to an allergen common to both deer and cat hair/dander. We concluded that atopic individuals sensitive to domestic animals may develop IgE-mediated reactions to deer or elk allergens following recreational or professional hunting contact with these animals.     

Sensitivity to common allergens: relation to respiratory symptoms and bronchial hyper-responsiveness in children from three different climatic areas of Australia

In order to examine further the relation between atopy, as defined by skin-prick tests, and respiratory illness, we studied three populations of schoolchildren aged 8-11 years and living in different climatic areas of New South Wales, Australia. Skin-prick tests were performed using 13 commercial allergen extracts. Respiratory and allergic symptoms were assessed using a self-administered questionnaire to parents and bronchial hyper-responsiveness (BHR) was measured by histamine inhalation test. We defined current asthma as BHR together with symptoms of wheeze in the 12 months prior to study. Children with one or more positive skin weals of greater than or equal to 3 mm had significantly more recent wheeze, hayfever, eczema and BHR than children with smaller weals (P less than 0.001). In each area, 95-97% of all atopic children were sensitized to one of the following seven allergens: house dust, Dermatophagoides farinae, D. pteronyssinus, cat dander, plantain, rye grass, and Alternaria tenuis. Thus, these seven selected allergen extracts and a skin weal of 3 mm could be used to detect clinically relevant atopy in these populations of children. Sensitivity to house dust mite had the strongest independent association with current asthma in all three areas. The associations of other allergen sensitivities with BHR or current asthma were area dependent, indicating the influence of local allergen levels on respiratory illness in children. The potency of house dust mite sensitivity in increasing the risk of children having BHR and current asthma is confirmed.     

Dissociation of house dust allergies. A comparison between skin tests, inhalation tests, specific IgE and basophil histamine release measurements.

The present study was undertaken to identify the most dominating allergens giving positive reactions both in vivo and in vitro, in patients with house dust (HD) hypersensitivity. Among 655 subjects with positive skin test reactions for HD, 469 (i.e., 71%) had positive reactions for Dermatophagoides pteronyssinus (D.pt.), and 186 (i.e., 28%) had negative reactions for D.pt.; among these 186 patients, 96% reacted to other different allergens, especially to animal epithelia. Challenge tests were performed in 52 patients. In 40 subjects with positive skin tests to HD and D.pt., all gave positive reactions to both tests. Among 12 patients, negative to D.pt. but positive to animal dander, provocation tests confirmed hypersensitivity to animal dander and absence of reaction after inhalation of D.pt. extract. Laboratory studies used specific IgE determinations (RAST Phadebas) and histamine release from human leukocytes. Of 240 HD-hypersensitive patients with serum IgE to HD, 204 also had positive RAST results for D.pt. and 36 for other allergens, there was a high incidence of cat dander (29/36). In a total of 13 dust-allergic people with positive skin tests for HD and D.pt., the relative cell sensitivity for these two extracts was determined from the allergen concentrations, which elicited 50% histamine release. The same biological parameters were determined in a group of 10 patients with positive skin tests to HD and cat dander, and negative skin tests to D.pt., for D.pt., HD, and cat dander extracts. Patients having positive skin tests to HD and D.pt. were also good histamine releasers for these two allergens. On the other hand, we could demonstrate that leukocytes from patients negative to D.pt. were really hypersensitive to cat dander. Our results demonstrate that neither HD skin tests nor HD RAST can characterize the effective allergens responsible for HD hypersensitivity. Identification of the major allergens present in HD, variable in each individual case, could aid toward more specific diagnosis.