Immunological features of asthma (Part II)

A serological comparison was made of two groups of 120 matched asthmatic and healthy subjects, between the ages of 20 and 49 years and matched for age and sex, in terms of serum total levels of IgG, IgM, IgA. IgD and IgE and of specific antibody levels in each immunoglobulin class to five common UK allergens. The relationship of clinical features to the serological tests was also examined in the asthmatic subjects. The following statistically significant findings were shown. The patients had higher levels than the controls of total globulins and of IgG, IgA and IgD but not IgM. In both patients and controls the females had higher IgM levels than the males. The total IgE levels were higher in patients than in the controls and the male patients had higher levels than the female patients. Total IgE levels were also related, to the numbers of first degree relatives with asthma, hay fever and eczema, to the severity of hay fever and to the amount of time off work in the male patients. In those male patients with exercise induced asthma the total IgE levels were lower than in those not showing this reaction. As for the other iminunoglobulins, the only significant differences were a higher [gG level in patients with FEV, or PFR>50% predicted and a higher IgD level in patients with hay fever. Radio-immunodiffusion tests for specific precipitins were positive for Dermatophagoldes pteronyssinus in comparable numbers of asthmatics (25.8%) and controls (21.7%). Positive precipitin tests were uncommon in tests with extracts of grass pollen, Aspergillus fumigatus, cat and dog hair in the patients and even less so in the controls. Positive RAST tests for specific IgE antibodies were obtained in patients and controls respectively, against D. pteronyssinus 59% and 11% grass pollen 37.0 and 12%, and A. fumigatus 6% and 4%. The male patients showed the closest significant relationship of specific IgE to D pteronyssinus and the history of house dust allergy, positive skin test and nasal test. in the females only the skin and specific IgE tests were related. Both sexes showed a significant association between specific IgE to grass pollen and positive skin tests and nasal tests, but only the males showed an association with the history. The size of skin test weal to D. pteronyssinus were related to the levels of specific IgE antibody, Correspondence: Professor J. Pepys, Cardiothoracic Institute, Brompton, London SW3 6HP. No differences were found between the four skin test groups and between the asthmatics and the control subjects in the incidence of bacterial precipitins and auin-antibodies.     

Passive cutaneous anaphylaxis (PCA) and specific IgE in cystic fibrosis and their heterozygotes

The serum from 75% of the patients with cystic fibrosis (C.F.) who had a positive prick test in their skin to at least one or more antigens, together with elevated concentrations of total serum IgE, also gave strong immediate PCA reactions in the baboon skin to Aspergillus fumigatus, bovine serum albumin and egg albumin. Of the C.F. patients, 37% also had elevated serum specific IgE to A. fumigatus whereas only 8–10% had either raised specific IgE or PCA reaction to Dermatophagoides pteronyssinus. Abolition of the PCA activity by incubating the C.F. sera or sputum at 56°C suggested that the reaginic antibody was IgE rather than IgG4. PCA reactions to a number of allergens could be detected in both the C.F. sputum and saliva. Several of the C.F. heterozygotes had a strongly positive history of allergy and a significant number of these heterozygotes had an elevated serum total IgE as well as positive PCA to Timothy grass pollen or to D. pteronyssinus similar to the patients with asthma or hay fever. Three C.F. patients who died gave strong prick test reactions to several allergens and their sera also had raised serum IgE and positive PCA to at least three different allergens, suggesting that immediate hypersensitivity is of some significance in patients with C.F.     

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.     

The prevalence of immediate positive skin tests to Dermatophagoides pteronyssinus and grass pollen in schoolchildren

The prevalence of immediate positive reactions to prick testing with house dust mite (Dermatophagoides pteronyssinus) and grass pollen allergens was determined in a random sample of 303 children aged between 8 and 14 years from two Southampton schools. One hundred and two (33.7%) showed positive reactions, fifty to both D. pteronyssinus and grass pollen, thirty to D. pteronyssinus only and twenty-two to pollen only. Allergic symptoms were present in fifty-one of the 102 children with positive skin tests; amongst thirty children with D. pteronyssinus skin sensitivity by itself, only six had symptoms suggestive of allergic disorder. Significantly more children with positive than with negative tests were reported by their parents to have suffered from recurrent bronchitis during early childhood.     

Identification of allergen-specific IgE antibodies in the sera of African asthmatics

Of eighty African asthmatics, sixty-three had significant levels of specific IgE against the house dust mite Dermatophagoides pteronyssinus. By contrast, grass-specific IgE was found in six patients and mould-specific IgE in none. Sixty-three patients also had symptoms predominantly during the rainy season. Positive skin tests against D. pteronyssinus correlated well with the presence of mite-specific IgE, as did the size of these skin test weals with the amount of specific IgE. For grass pollen and moulds there was no such relationship. There was no correlation between a history of sensitivity to house dust and either skin tests or specific IgE against D. pteronyssinus. The results support previous findings that it is allergy to house dust mite and not to grass pollens or moulds which is important in producing the seasonal symptoms in our patients.     

Determination of the stability of diluted allergen extracts using a concentration step prior to EAST inhibition

Background Generally the stability of diluted allergen extracts, as used for skin testing, provocation testing und immunotherapy can not be tneasured using a normal enzyme allergosorbent test (EAST) inhibition method. Objective The aim of this study was to determine the stability of diluted allergen extracts using an ultrafiltration step prior to the standard EAST inhibition procedure, in which the allergen extract was concentrated 100-fold. Methods This eoncentration procedure was validated for Dermatophagoides pteronyssinus, timothy pollen, birch pollen and cat dander extraets and used in a stability study in which three batches were stored for 1 year al 6° C and 25° C. Results There was no difference in relative potency before and after concentration of birch and timothy pollen extracts. D. pteronyssinus and cat dander extracts showed a significant decrease of 25% and 35% of the relative potency after concentration. The mean coeffieient of variation of 12 determinations of the stability study was 11.8%. Conclusion For all allergens the 30BU/mL or approximately 0.00025 mg/mL solution was stable for 12 months at both temperatures, except for D. pteronyssinus which declined rapidly at 25°C.     

Immunological studies in asthmatic children undergoing antigen provocation in the skin, lung and nose

In children with perennial asthma, dual (immediate and late) reactions in the skin to D. pteronyssinus and Timothy grass pollen were more frequent with high doses of antigen and were associated with large immediate reactions. The frequency of dual bronchial or nasal reactions was not related to the size of the immediate reaction and dual reactions were commonly elicited to the lowest antigen dose which would elicit an immediate reaction. Serum IgG, IgA, IgM or IgE concentrations, IgE or IgG antibodies to the antigens and defective yeast opsonization did not differ in children with dual or immediate only reactions in skin, nose or lung. In five patients undergoing bronchial provocation tests with D. pteronyssinus there was no fever, no fine crepitations in the kings and no significant change in the levels of C3.     

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.     

Clinical significance of specific IgE to common allergens

Serological measurements of specific IgE to Dermatophagoides farinae, D. pteronyssinus and grass pollen showed statistically highly significant correlations with prick test reactions, the sizes of weals elicited, nasal tests and the clinical history. In subjects with negative prick tests, intracutaneous tests gave reactions which were not associated with specific IgE or reactions to nasal tests. Highly significant correlations were also found between total IgE values and prick test reactions to the allergens tested and to 48/80 but not to histamine; there was a negative correlation with reactions to anti-IgE serum. The reactions to prick tests identified almost all subjects with specific IgE.     

<Emphasis Type="Italic">Dermatophagoides pteronyssinus</Emphasis> and <Emphasis Type="Italic">Tyrophagus putrescentiae</Emphasis> Allergy in Allergic Rhinitis Caused by Cross-reactivity Not Dual-Sensitization

Tyrophagus putrescentiae and Dermatophagoides pteronyssinus are causative factors for the development of airway hypersensitivity. The main objective in this study was to identify the cross-reactive allergens between T. putrescentiae and D. pteronyssinus and investigate their sensitization in patients with allergic rhinitis. The prevalence of sensitization to mites was determined by skin prick tests and histamine release assays. Both immunoblot and ELISA inhibition assays were performed by using the recombinant allergens of T. putrescentiae and D. pteronyssinus. The cross-reactive allergens were identified by using IgE-binding inhibition analysis. The correlations of specific IgE between T. putrescentiae and D. pteronyssinus to group 2 and group 3 mite allergens were compared. A total of 117 allergic rhinitis patients, aged between 16 and 40 years old were recruited to be included in this study. The results showed that 70% (82/117) of allergic rhinitis subjects had skin test positive reactions to D. pteronyssinus or T. putrescentiae. Among these mite-sensitive subjects, there were 81 subjects (81/82) sensitive to D. pteronyssinus and 34 subjects (34/82) sensitive to T. putrescentiae. Among the T. putrescentiae hypersensitive subjects, 97% (33/34) were also sensitized to D. pteronyssinus. In the IgE-binding inhibition analysis, 59% (13/22) subjects had IgE-binding activity of T. putrescentiae that was completely absorbed by D. pteronyssinus, especially components with MW at 16 kDa. In ELISA inhibition testing, 69% of IgE-binding was inhibited by rTyr p 2, and 45% inhibited by rTyr p 3. The titers of IgE antibodies to rTyr p 2 and rDer p 2 were well correlated, but not rTyr p 3 and rDer p 3. In conclusion, most T. putrescentiae sensitized subjects were also sensitized to D. pteronyssinus in young adult allergic rhinitis patients. The complete absorption of IgE binding activity by D. pteronyssinus indicates that T. putrescentiae hypersensitivity might be due to the cross-reactivity, not dual-sensitization of D. pteronyssinus and T. putrescentiae. The IgE-binding titers of group 2 allergens were well correlated and the binding activity of Tyr p 2 could be absorbed by Der p 2, suggesting that group 2 allergens are the major cross-reactive allergen of D. pteronyssinus and T. putrescentiae.     

IgE antibodies to house dust, mite, animal allergens and moulds in house dust hypersensitivity

Fifty-three patients were investigated by intradermal tests and Phadebas RAST and, in most cases, the serum IgE level was determined. They were tested for sensitivity to house dust, Dermatophagoides pteronyssinus, cat, dog, horse and mould allergens. All cases with IgE antibodies to house dust were found to have specific IgE to other tested allergens as well. Eighty-nine per cent of the patients being RAST positive for house dust were also positive for D. pteronyssinus and in the majority of those cases IgE antibodies to other allergens were detected. The results reaffirm previous findings that the mite is not the only allergen in house dust and that extract of house dust is a mixture of several allergenic substances, which make it less suitable for differential testing. It is concluded that serum IgE determination is of value as a screening procedure in the diagnosis and that the use of a number of specific allergens in RAST is valuable in pinpointing the offending allergen in house dust hypersensitivity.     

Lack of association between HLA-DQ and -DR genotypes and asthma in southern Chinese patients

Asthma is an inflammatory disease with a strong genetic predisposition. We have studied a group of unrelated asthmatic patients of southern Chinese origin on their HLA-DR and -DQ regions using molecular techniques and compared them with 104 healthy controls of the same ethnic origin. Restriction fragment length polymorphism (RFLP) was used to genotype the MHC class II DR β, DQ α and DQ β loci of the subjects. Polymerase chain reaction (PCR) using sequence specific primer (SSP) for DQ β genes was also performed. No significant difference was found in the HLA-DQ and -DR loci between the patients and the controls. All patients had their serum IgE antibody levels measured, bronchial reactivity assessed by histamine broncho-provocation and cutaneous reactivity to common allergens determined by skin-prick tests to Dermatophagoides pteronyssinus, Dermatophagoides farinae, mixed grass pollens, Aspergillus fumigatus, cat fur and dog dander and they were classified respectively. The HLA-DR and -DQ genotypes of these subgroups of patients were compared. There was no significant difference among these subgroups of patients according to their serum IgE levels, the degree of bronchial reactivity and whether they were positive for the skin tests for the various allergens respectively. The results suggest that HLA-DQ and -DR genotypes are not associated with asthma in southern Chinese people.     

Cow milk allergy within the spectrum of atopic disorders

In order to examine the relationship between cow milk allergy (CMA) and atopic disorders in childhood, a consecutive group of 42 infants with IgE mediated CMA was followed for at least 2 years. The incidence of sensitization to common food and inhalant antigens and the development of eczema, asthma, and food allergies was examined for the cohort and compared between patients whose CMA remitted and those with persistent disease. In this cohort the prevalence of eczema was 57%, asthma 69%, egg allergy 67%, peanut allergy 55%, and 83% of infants demonstrated positive skin-prick tests to three or more allergens. At the end of the study CMA had remitted in 13 patients (median age 44 months) whereas in 29 patients it persisted (median age 44 months). Although there was no significant difference in the incidence of eczema or asthma during the study between these two patient groups, the incidence of allergy to egg and peanut butter was significantly greater for children with persistent CMA. Consistent with our hypothesis that children with persistent CMA have a more severe dysregulation of IgE synthesis than those whose disease remits, patients with persistent CMA had a significantly higher incidence of and level of skin sensitivity to inhalant and other dietary allergens. Sensitization to the inhalant allergens Dermatophagoides pteronyssinus, cat dander and rye grass was frequently seen in early infancy and increased during the study period. Thus, children with IgE mediated CMA frequently generate IgE responses to multiple dietary and inhalant allergens in infancy and early childhood and develop immediate hypersensitivity to other foods as well as clinical eczema, and asthma.     

Specific IgA and IgE in childhood asthma, eczema and food allergy

Allergen-specific IgA and IgE antibodies were compared in 250 children with asthma (Dermatophagoides pteronyssinus, rye grass pollen), in eighty-six children with eczema (whole egg, cow's milk) and in two groups of children with egg and cow's milk allergy. In each of the conditions investigated, food allergy, asthma and eczema, increasing atopy was associated with increasing specific IgE levels to relevant allergens. There was no association of high IgE antibody levels with low IgA antibody levels in any of the conditions or allergens studied. There was, however, a tendency for subjects with more severe asthma to have high IgA levels with high IgE levels. IgA deficiency does not appear to be associated with atopic conditions of childhood.     

In vitro investigations in asthmatic children undergoing hyposensitization with tyrosine-adsorbed Dermatophagoides pteronyssinus antigen

Successful hyposensitization to Dermatophagoides pteronyssinus in perennial childhood asthma was associated with a slight mean rise of serum IgG antibody to the mite antigen in contrast to a placebo group in whom this antibody fell slightly. No relationship was detected between the effect on asthma and the magnitude of this change, Nor was there any consistent effect on IgE or IgA antibody. There was a wide range of total serum IgE and IgE, IgG and IgA antibody to D. pteronyssinus before treatment; this level did not predict the effect of treatment. Some patients lacked IgA antibody. IgE antibody to timothy grass pollen was raised in some but not others. These levels did not change systematically during the study and improvement occurred in those who had this antibody as well as IgE antibody to D. pteronyssinus. IgG and IgE antibodies to D. pteronyssinus were significantly correlated in the pre-treatment samples. Lymphocyte thymidine uptake was lower after 8 weeks of treatment than in the control group, not only after stimulus with D. pteronyssinus antigen, in vitro, but also with antigen from Candida albicans. This was not a serum effect. The late bronchial provocation response was lost only in those with serum IgA less than the log mean for age.     

IgE to food allergens are highly prevalent in patients allergic to pollens, with and without symptoms of food allergy

Serum samples from 274 patients allergic to one or more of three pollens (birch, grass, mugwort), from 36 patients allergic to cat and/or Dermatophagoides pteronyssinus but not to pollen and from 55 non-allergic controls, as well as 20 cord blood samples, were examined for specific IgE to six ‘pollen-associated’ food allergens In uiing a new sensitive assay (CAP). A questionnaire asking for reactions to food was also sent to all patients. In the pollen group, 111 patients (47%) were positive (≥0.71 kU/l) fora food allergen (392 positive tests). Of these, 92 were sensitive to apple, 68 to potato, 64 to carrot, 63 to celery, 61 to peach and 44 to melon. In the non-allergic group, no IgE to any of the food allergens tested was found, whereas in the group allergic to non-pollen allergens, only one individual had such an IgE. The CAP assay was found to he more sensitive than RAST for the allergens studied. A history of clinical reactions (oral symptoms in 67, rhinoconjunctivitis in 65, asthma in 42 and urticaria in 39) to the corresponding food allergen was reported mainly by patients with positive CAP. In conclusion, we found a high prevalence of IgE to some food allergens in patients allergic to pollen and Ihe absence of such antibodies in the control groups. The new in vitro assay, being moresensitue than previous ones, indicated a high prevalence of food specific IgE in pollen allergic patients, which in many cases did not correspond to clinical symptoms of food allergy.     

Exposure and sensitization to dust mite allergens among asthmatic children in Sao Paulo, Brazil

A group of 20 mite allergic asthmatic children aged 6-12 years old. living in Sao Paulo, Brazil, was studied regarding their degree of sensitization to house dust mites and exposure to mite allergens in their homes. In 18 out of 20 houses at least one dust sample was obtained which contained > 10 μg Der p I/g of dust. The highest levels of Dermatophagoides pteronyssinm allergens, Der p I and Group II, were measured in bedding samples (geometric mean 38.4 and 36.6 μg/g, respectively), followed by bedroom floor, TV room and kitchen. Mite allergen levels in Brazilian houses were as high as those reported to be associated with sensitization and acute attacks of asthma in other parts of the world. In keeping with previous reports that D. farinae is rarely found in Brazil, Der fl was undetectable or found in very low levels (<0.5 μg/g). Levels of cat allergen Pel d I of > 8 μg/g of dust were obtained only in 2 houses only. Cockroach allergen Bia g I was detected in five out of 20 houses. Levels of IgE antibodies to D. pteronyssinus were > 200 RAST U/ml in 19 out of 20 children (geometric mean 1588 RAST U/ml). IgE antibodies to cat, cockroach, A. fumigatus, ragweed and rye grass pollens were undetectable or <80 RAST U/ml. IgE antibodies to the mite Blomia tropicalix were also measured, and levels >200 RAST U/ml were observed in 13 out of 20 sera. Immunoabsorption studies demonstrated that the bulk of the IgE- antibody to B. tropicafis (64%) was to species-specific allergens and that 36% were cross-reactive with D. pteronyssinus. The implication of our results is that management of children with asthma in São Paulo should include skin testing for allergy to both Dermatophagoides and B. tropicalis as well as recommendations about environmental control of house dust mite exposure.     

Detection of allergen-specific IgE in tears of grass pollen-allergic patients with allergic rhinoconjunctivitis

Background Allergic conjunctivitis is a common symptom amongst Type I (IgE-mediated) allergic diseases; and mosl frequently seen as rhinoconjunctivitis. However, the site of production and the significance of allergen specific IgE needs further elucidation. Objective We investigated whether the presence of IgE in tears of grass pollen allergic patients correlated with disease and clinical symptoms, whether the IgE binding pattern to the different grass pollen antigens was diflferent in sera and tears, and whether IgA antibodies to grass pollen allergens were present in tears. Finally, we looked whether specific IgE was produced locally or was exudated from serum. Methods Sera from 44 grass pollen allergic patients suffering from either allergic rhinitis (n=11) or allergic rhinoconjunctivitis (n= 33) and from healthy controls (n= l) were used for the experiments. Binding of specific IgE and IgA antibodies to the differyent groups of grass pollen allergens (Phleum pratense) was evaluated by means of immunobtotting. Results Specific IgE was detected in sera as well as in tears of allergic patients, whereby tear-derived allergen-specific IgE exerted similar specificities to the corresponding IgE from serum. The correlation between symptoms of ocular allergy and the presence of allergen-specific IgE in tears was highly significant (P 0.0001). In contrast, only a poor correlation was found between specific and/or total IgE in sera and the manifestation of ocular allergy (P = 0.73). Conclusion Allergen-specific IgE antibodies in tears seem to be produced locally rather than exsudated from serum. IgE in tears seems to be responsible for allergic conjunctivitis. IgA in tears cannot exert a protective function since the IgA antibodies recognize different antigens in a grass pollen (Phleum pratense) extract than IgE antibodies. The highly significant correlation between allergic conjunctivitis and the presence of specific tear IgE emphasizes the diagnostic value of immunoblots with tear IgE, especially in cases in which serum provides inconclusive results.     

The allergen profile of beech and oak pollen

Background Beech and oak pollen are potential allergen sources with a world‐wide distribution. Objective We aimed to characterize the allergen profile of beech and oak pollen and to study cross‐reactivities with birch and grass pollen allergens. Methods Sera from tree pollen‐allergic patients with evidence for beech and oak pollen sensitization from Basel, Switzerland, (n=23) and sera from birch pollen‐allergic patients from Vienna, Austria, (n=26) were compared in immunoblot experiments for IgE reactivity to birch (Betula pendula syn. verrucosa), beech (Fagus sylvatica) and oak (Quercus alba) pollen allergens. Subsequently, beech and oak pollen allergens were characterized by IgE inhibition experiments with purified recombinant and natural allergens and with allergen‐specific antibody probes. Birch‐, beech‐ and oak pollen‐specific IgE levels were determined by ELISA. Results Beech and oak pollen contain allergens that cross‐react with the birch pollen allergens Bet v 1, Bet v 2 and Bet v 4 and with the berberine bridge enzyme‐like allergen Phl p 4 from timothy grass pollen. Sera from Swiss and Austrian patients exhibited similar IgE reactivity profiles to birch, beech and oak pollen extracts. IgE levels to beech and oak pollen allergens were lower than those to birch pollen allergens. Conclusion IgE reactivity to beech pollen is mainly due to cross‐reactivity with birch pollen allergens, and a Phl p 4‐like molecule represented another predominant IgE‐reactive structure in oak pollen. The characterization of beech and oak pollen allergens and their cross‐reactivity is important for the diagnosis and treatment of beech and oak pollen allergy.     

A clinical evaluation in children of the Pharmacia ImmunoCAP system for inhalant allergens

Background The Pharmacia ImmunoCAP system (CAP) for assaying serum IgE specific antibodies was evaluated in a clinical setting against skin-prick test (SPT) perfonncd using Dome/Hollister-Steir allergen extracts. The five cotnmon inhalant allergens D. pteronyssinus. D. farinae, mould mix, grass mix and cat epithelium were tested concurrently by both methods in 167 children aged 7.5–12 years. The specific SPT for D. pteronyssinus and D. farinae were also tested against the CAP house dust mite (HDM) mix. Objective The purpose of the study was to determine the sensitivity and specificity of the Pharmacia ImmunoCAP system Tor detecting serum IgE specific antibodies to inhalant allergens in a clinical setting, using the SPT result as the ‘gold standard’. Methods The SPTs were performed using Dome/Hollister-Steir allergen extracts. The serum IgE specific antibodies were quantitated using the radioimmunoassay version of the Pharmacia ImmunoCAP system. A history of allergic disease was assessed using a validated questionnaire. Results SPT gave more positive reactions than CAP with the exception of cat epithelium. The concordance between SPT and CAP results was 91% over all the tests. The concordance with SPT was slightly higher for the specific CAP for D. pteronyssinus and D. farinae (93% and 95% respectively) than for the CAP HDM mix (86% and 90% respectively). There was a higher proportion of positive results for both SPT and CAP in the 115 children defined as having a history of allergic disease. Using SPT defined allergy as the gold standard, the sensitivity of the CAP system was 87% for the two specific house dust mites but was lower for cat epithelium (67%), mould mix (59%) and grass mix (46%). The sensitivity of the CAP system improved for D. pteronyssinus (96%) and the HDM mix (91%) when tested in subjects defined as having a history of allergy associated disease. The specificity of the CAP system showed less variation between allergens and ranged from 90–99%. Conclusion The results of this study of children aged 7.5–12 years demonstrate that, for the inhalent allergens tested, the Pharmacia ImmunoCAP system perfoms well in the setting of known allergic disease.