ABSTRACT
Allergic rhinitis and asthma share common epidemiological features and inflammatory processes. The aim of the present study was to document the influence of natural allergen exposure in exhaled NO [eNO] and in spirometric parameters of patients with seasonal allergic rhinitis[SAR] and to investigate the differences among subjects with positive versus negative bronchial provocation to metacholine [BP[Mch]]. Twenty-six non-smoking patients [13F/13M; mean age 28.4ys] with a documented history of SAR, 15 healthy, non-atopic [6F/9M; mean age 37.1ys] and 6 non-symptomatic atopic subjects [3F/3M; mean age 36.5ys] were studied. At the first visit during pollen season each subject filled symptom-score card, underwent eNO and nasal NO [nNO] measurements and spirometry. BP[Mch] was performed within the next 10 days. At the second visit out of pollen season, all measurements but BP[Mch] were repeated. Control subjects underwent eNO and nNO measurements. eNO was significantly increased during pollen season in BP[Mch] positive vs BP[Mch] negative [46.22 +/- 32.60 vs 17.81 +/- 12.67, p=0.014] and vs non-atopic controls [11.40 +/- 5.84, p<0.001] as well as atopic controls [13.56 +/- 5.34, p=0.001]. No difference was detected out of pollen season in both patients' groups. nNO values were increased only in BP[Mch] [+] group compared to both control groups in pollen season [vs non-atopies p=0.002, vs atopies p=0.002] and only vs non-atopies out of season, p=0.004. Regression analysis has shown that the difference in FEF 25-75 values [off season-in season] is a predictor of positive BP[Mch]. eNO is markedly increased in BP[Mch] patients with allergic rhinitis while mid-expiratory flow may represent an early marker of lower airway involvement in respiratory allergy