Are the most common food allergens in an Iranian atopic population compatible with worldwide reports? A systemic review and meta-analysis with molecular classification of frequent allergens.

BACKGROUND: Undesirable immunological responses to alimentary allergens are one of the hallmarks of atopic diseases. The prevalence of common food allergens is dissimilar among different communities with distinct nutritional habits and genetic characteristics. AIM: To assess the prevalence of the most common food allergens in Iran, using different reliable studies. METHODS: All studies determining sensitization to common food allergens that were indexed in PubMed, Web of Science, Google Scholar, ProQuest, Scopus, Iran Medex, and Magiran were included in this review. To perform a meta-analysis, STATA 14 and metaprop command was applied. A logistic-normal random-effects model with Freeman-Tukey double arcsin transformation was applied to combine the findings of different studies and evaluate their heterogeneity. Random pooled estimate (ES) (pooled prevalence), 95% confidence interval (95% CI) and p-value were determined. RESULTS: A total of 23 studies with data from a total of 6126 children and adults met the inclusion criteria for entering this meta-analysis. The respective pooled prevalence of a positive family history of allergy and positive specific IgE to at least one food allergen was 72% (95% CI: 66-77%) and 41% (95% CI: 33-49%), respectively. Our results in the total population revealed that allergic sensitization to egg yolk, cow's milk (CM), egg white, and wheat were 25% (95% CI: 16%-35%), 24% (95% CI: 19-29%), 23% (95% CI: 18%-28%), and 9% (95% CI: 6%-14%), respectively. Walnut, peanut, and soybean sensitization was detected in 23% (95% CI: 17%-31%), 23% (95% CI: 13%-33%), and 20% (95% CI: 12%-28%) of patients, respectively. Random pooled ES for sensitization to shrimp and fish was 32% (95% CI: 21-45%) and 12% (95% CI: 6-20%), respectively. The result of analysis in different age groups revealed that allergic sensitization to milk, egg white, and egg yolk declines in higher age groups; while shrimp sensitization increases in older patients. In patients with atopic dermatitis, egg white was the most frequent food allergen 29% (95% CI = 18-42%); while wheat was the least frequent 8% (95% CI = 4-14%). CONCLUSIONS: Considering the prevalence of different food allergens, the results of the current meta-analysis revealed that egg yolk and cow's milk had the second and third rate after shrimp, respectively. The high prevalence of sensitization to shrimp may be attributed to its high consumption in coastal areas and/or cross-reactivity of shrimp with some aeroallergens such as mites.

The Study of Total IgE Reference Range in Healthy Adults in Tehran, Iran.

BACKGROUND: IgE is an antibody class that regarded as an important factor in the pathogenesis of allergic diseases, asthma, immune responses to parasitic infection and it could be responsible for the late- phase allergic response. The objective of this study was to evaluate total IgE in healthy Iranian adults, establishment of reference range of total IgE and assess helpfulness of this value in clinical diagnosis atopic and allergic diseases. METHOD: Three hundred sixty six healthy adults from blood transfusion volunteers (18 to 60 years) were selected in this study. A specific questionnaire (including demographic factors, smoking status and …) was filled out for each person. Also, we evaluated effect of race and education on total IgE. These adults had no history of allergic disease. The total serum IgE level using a commercial enzyme immunoassay and CBC (Eosinophil count) was determined in them. RESULTS: Mean of age was 37.32± 10.93 yrs and 219 cases were males and 147 females. The geometric mean of total IgE was 20.84 IU/ml (2-373 IU/ml) (95% percentile= 250) (95% confidence interval=46.27-62.70). No differences was observed between mean of IgE log in males and females (P= NS) but mean of total IgE log in females is more than males. CONCLUSION: Normal range of serum total IgE obtained in this study could be helpful for diagnosis of IgE-dependent allergic disease, as reference ranges in Iranian healthy adults.