Diagnostic use of enzymatic RAST skin tests and determination of eosinophils in nasal mucosa in allergic rhinitis

AIMS: Allergic rhinitis is the most frequent disease mediated by immunoglobulin E (IgE). Nasal challenge is the gold standard for the diagnosis of allergic rhinitis. Skin tests (ST) are the most used diagnostic method to detect the presence of specific IgE bind to skin mast cells. The exposition of the nasal mucous membrane to the allergen is followed by an increase of the local eosinophils; the count of eosinophils in nasal mucous (ENM) is a diagnostic test for allergic rhinitis. Enzymatic RAST or enzymatic allergo-sorbent test (ESA) measures the level of serum allergen-specific IgE. OBJECTIVE: To measure the sensitivity, specificity, and diagnostic precision of ST, EAST and ENM in allergic rhinitis. METHOD: We studied 241 individuals, 162 of them had allergic rhinitis, and 79 were healthy controls. They underwent nasal challenge and intradermic ST for Dermatophagoies spp (acarus). Fraxinus americana (Ash-tree), Amaranthus palmieri (quelite), Cynodon Dactylon (capriola) and Felis catus (cat), EAST for Dermatophagoides pteronyssinus (acarus), and ENIVI. Results of ST, EAST and ENIVI were compared with their corresponding nasal challenge, and the prevalence of allergic rhinitis for each allergen was calculated. The best cut point was assessed by means of receiver-operator curves (ROC), and sensitivity, specificity, positive predictive value, negative predictive value, inter-observer concordance coefficient, area under ROC (0), standard error of 0 (SEO), and 95% confidence interval of 0 of each test were calculated using the best cut point. RESULTS: ST and EAST had the best sensitivity and specificity. ENM had the lowest sensitivity and specificity. CONCLUSION: For the diagnosis of Dermatophagoides spp allergic rhinitis ST for Dermatophagoides spp and EAST for Dermatophagoides pteronyssinus have the same diagnostic precision. According to the indexes for diagnostic precision, and inter-observer concordance coefficient, ST and EAST are useful to diagnose allergic rhinitis induced by the evaluated allergens. ENIVI is a test that is not very useful for the diagnosis of allergic rhinitis.