Differences and similarities between allergic and nonallergic rhinitis in a large sample of adult patients with rhinitis symptoms.

Background: Allergic rhinitis (AR) and nonallergic rhinitis (NAR) may present with different clinical and laboratory characteristics.

Methods: A total of 1,511 consecutive patients, aged 18-81 years, diagnosed with rhinitis, 56% females and 44% males, underwent complete allergic evaluation including skin prick test, blood eosinophil counts, nasal eosinophil counts, peak nasal inspiratory flow (PNIF) measurement and evaluation of nasal symptoms using a visual analog scale (VAS).

Results: A total of 1,107 patients (73%)had AR, whereas 404 (27%) had NAR. Patients with NAR were older and predominantly female. A higher nasal eosinophils count was associated with AR and a lack of clinical response to antihistamines. AR patients had more sneezing and nasal pruritus, whereas NAR was characterized mainly by nasal obstruction and rhinorrhea. AR patients had more severe symptoms and recurrent conjunctivitis, whereas NAR patients had slightly more frequent episodes of recurring headaches as well as olfactory dysfunction. PNIF, blood eosinophil counts and VAS of nasal symptoms were higher in patients with AR. In a final logistic regression model, 10 variables were statistically different between AR and NAR: age [OR 0.97 (95% CI 0.96-0.98)], sneezing [OR 4.09 (95% CI 2.78-6.00)], nasal pruritus [OR 3.84 (95% CI 2.60-5.67)], mild symptoms [OR 0.21 (95% CI 0.09-0.49)], intermittent/severe nasal symptoms [OR 3.66 (95% CI 2.06-6.50)], VAS [OR 1.06 (95% CI 1.04-1.08)], clinical response to antihistamines [OR 22.59 (95% CI 13.79-37.00)], conjunctivitis [OR 4.49 (95% CI 2.86-7.05)], PNIF [OR 1.01 (95% CI 1.00-1.01)] and nasal eosinophil counts [OR 1.14 (95% CI 1.10-1.18)]. Receiver operating characteristic analysis showed high predictive accuracy for a model including these variables independently of the diagnosis of AR/NAR (cutoff <0.74).

Conclusions: We showed that the several clinical and laboratory parameters reported above may help to reinforce or exclude the diagnosis of AR obtained with skin prick test.