Discriminant analysis in allergic rhinitis and asthma: methacholine dose–response slope allows a good differentiation between mild asthma and rhinitis

Abstract

Asthma and rhinitis frequently coexist in allergic patients, but nasal symptoms may predominate, leading to asthma underdiagnosis and undertreatment. Discriminant analysis obtains the best differentiation between groups using one or one set of variables. Our aim was to identify the laboratory test [allergen exposure, total and specific serum IgE, lung function, blood eosinophils and, bronchial response and sensitivity to methacholine (Mth) and allergen] or combination of them that allowed the best differentiation between mild asthma and allergic rhinitis. A cross-sectional analysis was performed in 86 Dermatophogoides pteronyssinus allergic rhinitis patients, who were classified according to clinical data as rhinitis plus mild asthma (n = 62) or "pure" rhinitis (n = 24). Bronchial symptoms had been exhaustively evaluated during a 2-years pre-inclusion period. Patients underwent skin tests and bronchial challenge with Mth and allergen. The exposure to D. pteronyssinus allergen (Der pl) was quantified in dust samples. Dose-response curves with Mth [until the FEV1 fell by 40% or the maximal dose (200 mg/ml) was inhaled] were attained. We developed multiple models of discriminant analysis in order to evaluate the capacity of the above variables to differentiate groups. Asthma patients had higher total and specific IgE levels and a greater sensitivity (PD20 values) and response [dose-response slope (DRS)] to both Mth and allergen. The model entering these variables was the one that correctly classified more patients (79.2%). The discriminative power of the model that only included Mth-DRS values was similar to the above (78.8%). Bronchial response to Mth is quantitatively different in allergic rhinitis patients who display mild asthma symptoms when compared to those that only report rhinitis, suggesting a distinct bronchial intrinsic behavior. The utilization of complete dose-response curves with Mth allows a good separation between mild asthma and "pure" rhinitis patients and might be useful in the diagnosis of mild asthma. Whether the early detection and treatment of these patients prevents the development of symptomatic asthma needs further evaluation.

Total serum immunoglobulin E levels in a case–control study in asthmatic/allergic patients, their family members, and healthy subjects from India

“…Wittig et al [23] reported that overlaps of serum IgE with normal values (of healthy volunteers) are the largest for patients of urticaria, eczema, and AR, and the least for patients with allergic asthma. A number of workers have also observed a significant difference between the IgE levels of asthmatics and AR patients in different populations [23][24][25][26]. However, the severity of AR was not taken into account in the present study and it is possible that the marked difference observed between IgE levels in asthma and rhinitis patients could be due to the fact that most of the patients of AR might be having mild to moderate rhinitis.…”

Age of onset and the characteristics of asthma

“…It is possible that some of the patients had coexistent asthma and rhinitis, but with nasal symptoms predominating, leading to an underdiagnosis and undertreatment of asthma 21 . Underdiagnosis by the GP has been reported in only 21% of cases, but poor perception of dyspnoea by the patient can cause up to a 66% underpresentation of respiratory symptoms 22 .…”

Allergic Rhinitis and its Impact on Asthma (ARIA) 2008*

“…Discriminant analysis in allergic rhinitis and asthma can be obtained from the methacholine dose-response (1931).…”