Lower respiratory tract complications during nasal provocation: nonspecific stimulant or specific allergen?

Allergic rhinitis (AR) is an allergic inflammatory disease in which allergen exposure leads to the appearance of symptoms in sensitized individuals because of histamine liberation from nasal mucosal mast cells. Comorbidity of this disease with allergic asthma is common. Therefore, the one airway one disease theory has been put forward. Lower respiratory tract provocation tests with both nonspecific (methacholine) and specific stimulants (allergen) have yielded positive results in nonasthmatic patients with AR. However, not enough research is available to demonstrate whether there is a response in the lower respiratory tract during nasal provocation tests (NPTs) performed to evaluate only nasal airway in these patients.

To determine if the lower respiratory tract was affected as a result of NPTs with nonspecific and specific stimulants in nonasthmatic patients with AR and to determine the frequency of lower respiratory tract obstruction due to NPT with nonspecific and specific stimulants.

Thirty-six participants were enrolled in the study between November 2005 and January 2006 (18 AR patients and 18 healthy control subjects). Patients underwent 2 sessions of NPT. The first session was performed with nasal methacholine as a nonspecific stimulant, and the second session was performed with nasal Olea europaea extract as a specific stimulant. The control group underwent only nonspecific nasal provocation with methacholine. Basal nasal opening and nasal pressures were evaluated spirometrically by rhinomanometric measurements and basal respiratory function tests in both groups before methacholine nasal provocation. Whether or not nasal provocation was achieved, spirometric measurements were performed in all patients and controls after NPTs.

NPTs with methacholine resulted in a similar frequency of nasal provocation in the patient and control groups (P = .63). However, the mean methacholine dose was lower in patients with AR (P = .049). There was a decrease in parameters of asthma, including the ratio of forced expiratory volume in 1 second to forced vital capacity (P = .04), peak expiratory flow (P = .01), and forced expiratory flow between 25% and 75% (P = .004), as a result of NPTs with methacholine in the patient group. However, NPTs with allergen did not cause a change in lower respiratory tract obstruction criteria.

Lower respiratory tract obstruction can occur after NPTs with nonspecific stimulants; therefore, tests performed with specific allergens can be regarded as safer.