ELISA in diagnosis of respiratory allergy. A comparison with RAST and skin tests

IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper

Currently, testing for immunoglobulin E (IgE) sensitization is the cornerstone of diagnostic evaluation in suspected allergic conditions. This review provides a thorough and updated critical appraisal of the most frequently used diagnostic tests, both in vivo and in vitro. It discusses skin tests, challenges, and serological and cellular in vitro tests, and provides an overview of indications, advantages and disadvantages of each in conditions such as respiratory, food, venom, drug, and occupational allergy. Skin prick testing remains the first line approach in most instances; the added value of serum specific IgE to whole allergen extracts or components, as well as the role of basophil activation tests, is evaluated. Unproven, non-validated, diagnostic tests are also discussed. Throughout the review, the reader must bear in mind the relevance of differentiating between sensitization and allergy; the latter entails not only allergic sensitization, but also clinically relevant symptoms triggered by the culprit allergen.

A paper-based chemiluminescence immunoassay device for rapid and high-throughput detection of allergen-specific IgE

The fast and precise detection of potential allergen-specific immunoglobulin E (sIgE) is imperative for the diagnosis and appropriate treatment of allergic diseases. In this study, we have successfully fabricated a novel paper-based immunoassay device for the detection of sIgE in allergic diseases. We used Can f 1, one of the main dog allergens, as a model allergen to detect sIgE in human sera. To achieve excellent performance, the experimental parameters were optimized. Further, we extended this device for potential applications in the clinical diagnosis of allergic diseases: worthwhile clinical performance in the detection of allergens was achieved as compared to that achieved by commercial enzyme-linked immunosorbent assay (ELISA) kit. Therefore, it was proven that this strategy has the advantages of high-throughput, rapid, sensitive, and highly accurate detection of trace amounts of sIgEs. Furthermore, by simply changing the antigen and antibody, this device could be used for the high-throughput detection of other allergens, so as to achieve multiallergen detection and appropriate desensitization therapy, thereby making it promising in the determination of allergic diseases in clinics.

The accuracy of features in the clinical history for predicting atopic sensitization to airborne allergens in children

BACKGROUND

The clinical history is given considerable weight when one decides which allergens are responsible for a patient's symptoms, and in research studies the clinical history has been used as the "gold standard" with which different tests for allergy are compared.

OBJECTIVES

To determine whether standardized questions accurately predict replies to detailed questions asked by an experienced allergist, and to assess the utility of certain standardized questions for predicting sensitization to individual allergen groups.

METHODS

Trained interviewers put standardized questions to parents of 1160 children, aged 1 to 17 years, who had respiratory symptoms and had been newly referred to the allergy clinic of a children's hospital. For the first 151 of the subjects the answers were compared with those elicited by questions asked by a pediatric allergist. Skin prick tests and pollen counts were performed by a technologist.

RESULTS

The standardized questions had an accuracy for predicting the allergist's history of 93% to 97% for all questions except one. The standardized questions with the highest accuracy for predicting the skin test results to the appropriate allergens were the following: for mite, improvement in symptoms when outdoors (66.8%) and when in dry areas 69.4%), and aggravation during house cleaning (65.9%) and when bed making (70.6%); for dog, symptoms when with dogs (80.6%); for cat, symptoms when with cats (77.3%); for tree pollen, symptoms worse in April (70.8%) and when among trees in March and April (80.8%); and for grass pollen, exacerbation in June (69.2l%) and during lawn mowing (71.2%). Although specificity was generally above 80%, sensitivity was variable, ranging from 11% to 56%.

CONCLUSIONS

The standardized questions accurately predicted a detailed history obtained by an experienced allergist. Because standardized questions are reproducible they are the preferred method of history taking for research projects. Because several of the standardized questions have a high specificity they are useful for excluding sensitization to individual allergen groups, but because they have only a modest sensitivity, they are less helpful for detecting those who are sensitized to individual allergen groups.

Sensitization to Ganoderma lucidum in patients with respiratory allergy in India

Although human sensitization to basidiomycete Ganoderma has been reported in New Zealand, North America and Europe, hypersensitivity due to this fungi is not known in India, in spite of its prevalence in the atmosphere. We have studied the atmospheric concentration of Ganoderma in different localities within Delhi and the sensitization level to this fungi amongst the Indian population. Aerobiological sampling, using a Burkard personal slide sampler, was carried out in Delhi for 2 consecutive years (October 1989-September 1991). The sampler was operated at 10 day regular intervals for 10 min to trap the spores. The peak season for Ganoderma is recorded from July to September with highest average monthly catch of 336 spores/m3 in September 1991 from south Delhi. Antigenic extracts were prepared from both, the spores and whole body of Ganoderma lucidum. The results of intradermal skin tests conducted on 172 patients revealed that 28.48% and 17.44% of patients showed marked skin reactivity to spore and whole body extracts, respectively. A significant correlation (r = 0.963, P < 0.01) was found between intradermal and skin-prick tests. More than 80% of the intradermal test positive patients had significantly (P < 0.01) elevated IgE antibodies to the fungi in question. Thus, sensitization to Ganoderma lucidum has been reported for the first time in the atopic population of India.

Comparison of four in vitro assays for specific IgE detection

Three immunoenzymatic techniques for specific IgE detection (Pharmacia CAP System, Kallestad Allercoat System, Neo Abellò Hamlet-IgE) and the classical Phadebas RAST were compared using 34 sera from patients with a clinical diagnosis of allergic disease and 19 sera from healthy non-atopic controls. IgE antibodies to 9 aeroallergens and 6 food antigens were assessed and 399 tests were run with each method. All techniques showed a high specificity (92%-100%) and satisfactory efficiency (82%-98%), while the sensitivity for RAST, CAP, Allercoat and Hamlet was 89%, 91%, 83% and 53%, respectively, with the lowest values for food allergens. There was a good overall correlation of the four techniques, except when the Hamlet method was compared with the other methods for food-specific IgE detection (correlation coefficient < 0.3). These data indicate that CAP, Allercoat and RAST are satisfactory techniques for specific IgE determination, either for inhalants or for food allergens; CAP, however, offers the highest sensitivity without loss of specificity.

Management of allergic rhinitis: focus on intranasal agents

The clinical manifestations of allergic rhinitis are the result of an immune-mediated process after exposure of a sensitized individual to airborne allergens. The primary symptomatology includes nasal congestion, rhinorrhea, nasal and conjunctival pruritus, and sneezing. Principles of management include allergen avoidance, palliative therapy, immunotherapy, and pharmacotherapy. Oral decongestants stimulate alpha-adrenergic receptors in the nasal cavity, resulting in vasoconstriction and decreased edema. Oral antihistamines block histamine1 (H1) receptors, and may relieve rhinorrhea, sneezing, and nasal and conjunctival pruritus. Topical decongestants have a local effect on adrenergic receptors in the nasal mucosa, resulting in rapid, marked vasoconstriction. Intranasal corticosteroids inhibit mediator release from mast cells and basophils, and reduce edema of the nasal mucosa. Dexamethasone sodium phosphate, beclomethasone dipropionate, and flunisolide are currently available for intranasal administration. Cromolyn sodium inhibits allergen-induced degranulation and mediator release from sensitized cells, and is useful primarily as a prophylactic agent. Several agents, including the corticosteroids budesonide and flucortin butylester, the mast cell-stabilizing agent nedocromil sodium, the anticholinergic agent ipratropium bromide, and the H1 receptor antagonist levocabastine are being investigated for intranasal use in the management of allergic rhinitis.

Evidence of allergic hypersensitivity to chironomid midges in an English village community

Some chironomid (non-biting) midges contain potent human allergens, principally in the form of insect haemoglobins. In view of previously demonstrated immunological cross-reactivity between some different midge species, the possible role of British midges in allergic disease was studied. The chosen site, Farmoor near Oxford, is a village that has been subject to several annual nuisance midge swarms since the construction of an adjacent water-supply reservoir in 1964, which was extended in 1975. The incidence and severity of hypersensitivity in the community was assessed by questionnaire survey, skin-prick testing, radio-allergosorbent tests (RAST) and RAST inhibition, and enzyme-linked immunosorbent assays (ELISA) and ELISA inhibition, using extracts of locally caught adult midges (Tanytarsus sylvaticus, T. bathophilus and Chironomus anthracinus) and laboratory cultured larvae (C. riparius). These tests revealed a low but significant level of midge-related hypersensitivity with skin-prick results showing seasonal fluctuations, but this seasonality was not confirmed with an IgE RAST. A correlation between IgE levels and relevant symptoms was found (P less than 0.01) using RAST, but not between IgE and skin-test results. Enzyme-linked immunosorbent assay results did not correlate with any other parameter measured. The incidence and severity of allergic reactions to the midges tested in this community was low.