Cellular in vitro assays in the diagnosis of Hymenoptera venom allergy

BACKGROUND: The current diagnostic procedures of anaphylactic reactions to hymenoptera stings include intradermal tests, venom-specific IgE (sIgE) and possibly sting challenge tests. Sometimes, the culprit insect remains unidentified. The usefulness of the cellular assays CAST-ELISA and Flow-CAST in the management of hymenoptera venom allergy was investigated. METHODS: 134 patients with systemic reactions after a yellow jacket wasp and/or honey bee sting and 44 healthy controls underwent skin tests, as well as determination of sIgE (CAP-FEIA), leukocyte sulfidoleukotriene release (CAST-ELISA) and basophil CD63 expression (Flow-CAST) upon insect venom stimulation. The clinical diagnosis based on the history alone served as reference. Sensitivity, specificity, and positive and negative predictive value of all methods were compared. Concordance and correlations among methods were calculated. RESULTS: Sensitivity and specificity of all in vitro tests were consistently high. The combination of all tests (skin tests, sIgE, combined cellular assays) yielded a positive predictive value of 100% for both venoms, if all 3 were positive, and a negative predictive value of 100%, if at least 1 test was positive. Relative specificities were considerably higher for the cellular assays (honey bee: CAST 91.1%, Flow-CAST 85.7%; yellow jacket wasp: CAST 98.4%, Flow-CAST 92.1%) and allow the detection of the culprit insect in patients with reactivity to both insects. The concordance between methods was good. There is no correlation between severity of clinical reaction and cellular assays. CONCLUSION: CAST-ELISA and Flow-CAST are valuable additional diagnostic tools for establishing the true culprit insect in patients with unclear clinical history or sensitization to both insects

Development and validation of a health-related quality-of-life questionnaire in patients with yellow jacket allergy

Background: The effects of an anaphylactic reaction after a yellow jacket sting on health-related quality of life (HRQL) have not been studied and are thus unknown. Objective: Development of a disease-specific instrument to measure HRQL in patients with yellow jacket allergy and validation of this instrument both cross-sectionally and longitudinally. Methods: Quality-of-life items were generated from patient interviews. Items with the highest impact were considered and correlated cross-sectionally with an independent measure (consisting of 2 questions in which patients were asked what they expected would happen if they were stung again, "Expectation of Outcome" questionnaire). Cross-sectional and longitudinal validation was achieved by administering this instrument to 69 Dutch patients. The questionnaire was also administered to 50 patients with yellow,jacket allergy in Baltimore, Maryland, to establish cross-sectional validity of the English version. Results: The survey showed that patients experienced impairment in quality of life especially because of emotional distress. The resultant questionnaire has 14 items. The cross-sectional validation yielded a correlation coefficient of 0.69 for the Dutch version and 0.56 for the English version. The longitudinal validation yielded a correlation coefficient of 0.71. The responsiveness of this instrument was demonstrated by the questionnaire's ability to detect changes over time. It may be completed in approximately 10 minutes by patients without assistance. Conclusion: Patients with yellow jacket allergy experience impairment in quality of life especially because of emotional distress. It has, been possible to develop and validate a questionnaire (the Vespid Allergy Quality of Life Questionnaire) by which the HRQL of these patients can be measured. The instrument may be administered rapidly and is easy to use

Skin testing technique and precision in stinging insect allergy

Aim. We report on quantitative analysis of skin tests in patients undergoing Hymenoptera venom immunotherapy. The need for accuracy, coupled with a sound manual technique, in performing this procedure is emphasized. Involuntary errors may occur and pose serious problems with interpretation of results. A revealing example is reported and the strategy devised to analyse the flaws and overcome the resulting problems is presented and discussed. Background. Skin testing plays a key role in the diagnosis of most allergic disease and in the assessment of allergen immunotherapy. Particularly, insect sting allergy requires implementation of complex and demanding skin testing protocols and a competent nursing practice. Methods. Sixteen patients were tested before starting the immunotherapy and after three years of treatment. Cutaneous response (expected to decline, following immunotherapy) was assessed as: (i) allergen-elicited wheal areas; (ii) ratios between allergen- elicited wheal areas and homologous histamine (positive controls) wheal areas. Results. By using allergen-elicited areas, the paradoxical result was obtained that skin reactivity had increased instead of decreasing, upon immunotherapy. Histamine response analysis suggested that this paradox might rather be the result of a technical flaw. Analysis of written notes of routine clinical meetings revealed that an importantmanual flaw had been detected (and corrected) some years earlier, affecting the results of the baseline testing (viz. the allergen was injected deeper in the skin, yielding a weaker response). Skin reactivity evaluation in terms of allergen–histamine ratio confirmed this interpretation, as, when the baseline ratios were compared with the three years immunotherapy ratios, a distinct decline in skin reactivity was detected, as expected. Conclusions. Skin testing in insect sting allergy is a conceptually and manually complex procedure, which should be subjected to systematic quality control assessment, like a laboratory procedure. The personnel involved in the performance of this procedure should receive appropriate and extensive training. Relevance to clinical practice. Diagnosis of allergic diseases and monitoring of immunotherapy largely rely on impeccable skin testing technique