[Diagnosis of NARES by methacholine nasal provocative test]

Non-allergic rhinitis with eosinophilia syndrome (NARES) is defined as chronic rhinitis in which no specific allergens are identified although allergic symptoms occur throughout the year and nasal smears are positive for eosinophils. This rhinitis is not type I allergy, and the methacholine provocative test for the lower airways is negative. In this study, we performed the nasal methacholine provocative test using an astrograph, as well as allergen skin testing, IgE RAST determination, assessment of eosinophil counts in nasal smears, and the allergen nasal provocative test in 101 patients with perennial chronic rhinitis. This study attempted to make a differential diagnosis of NARES and to characterize this disease in comparison with other types of chronic rhinitis. Among the 101 subjects, 58 patients (57.4%), 17 (16.8%), and 26 (25.8%) were respectively classified into Group I (the nasal allergy group), Group II (the NARES group), and Group III (the vasomotor rhinitis group: VMR group). Blood eosinophil counts and serum IgE RIST levels were lower in Group II than in Group I. There were no differences in respiratory function among the 3 groups before the nasal methacholine provocative test. Respiratory function decreased in Group I with methacholine provocation, but remained unchanged in Groups II and III. Based on the above findings, hypersensitivity to methacholine was noted in both the upper and lower airways of patients with nasal allergy, only in the upper airway of VMR patients, but in neither the upper nor the lower airways of NARES patients. This indicates that the nasal methacholine provocative test may be useful in waking a differential diagnosis in cases of chronic rhinitis.