Which test is most useful in diagnosis of allergic rhinitis?

An accurately applied skin test is the most valuable tool for identifying the causative antigen in allergic rhinitis, yielding results in approximately 20-30 minutes. The radioallergosorbent test (RAST), albeit accurate, is more expensive and less discriminative than skin testing. Elevated immunoglobulin E (IgE) levels are observed in only 30%-40% of patients with allergic rhinitis and may be secondary to other unrelated disorders. Although eosinophils are usually identified in nasal secretions from patients with allergic rhinitis, they are also detected in eosinophilic nonallergic rhinitis and hyperplastic sinusitis. peripheral eosinophilia seen in a peripheral blood smear is an inconsistent finding.