Dissociation between skin test reactivity and anti-aeroallergen IgE: Determinants among urban Brazilian children.

BACKGROUND: The dissociation between specific IgE and skin prick test reactivity to aeroallergens, a common finding in populations living in low and middle-income countries, has important implications for the diagnosis and treatment of allergic diseases. Few studies have investigated the determinants of this dissociation. In the present study, we explored potential factors explaining this dissociation in children living in an urban area of Northeast Brazil, focusing in particular on factors associated with poor hygiene. METHODS: Of 1445 children from low income communities, investigated for risk factors of allergies, we studied 481 with specific IgE antibodies to any of Blomia tropicalis, Dermatophagoides pteronyssinus, Periplaneta americana and Blatella germanica allergens. Data on demographic, environmental and social exposures were collected by questionnaire; serum IgG and stool examinations were done to detect current or past infections with viral, bacterial, protozoan and intestinal helminth pathogens. We measured atopy by skin prick testing (SPT) and specific IgE (sIgE) to aerollergens in serum (by ImmunoCAP). SIgE reactivity to B. tropicalis extract depleted of carbohydrates was measured by an in-house ELISA. Total IgE was measured by in house capture ELISA. SNPs were typed using Illumina Omni 2.5. RESULTS: Negative skin prick tests in the presence of specific IgE antibodies were frequent. Factors independently associated with a reduced frequency of positive skin prick tests were large number of siblings, the presence of IgG to herpes simplex virus, Ascaris lumbricoides and Trichuris trichiura infections, living in neighborhoods with infrequent garbage collection, presence of rodents and cats in the household and sIgE reactivity to glycosylated B. tropicalis allergens. Also, SNP on IGHE (rs61737468) was negatively associated with SPT reactivity. CONCLUSIONS: A variety of factors were found to be associated with decreased frequency of SPT such as unhygienic living conditions, infections, total IgE, IgE response to glycosylated allergens and genetic polymorphisms, indicating that multiple mechanisms may be involved. Our data, showing that exposures to an unhygienic environment and childhood infections modulate immediate allergen skin test reactivity, provide support for the "hygiene hypothesis"

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