Added value with extended NO analysis in atopy and asthma

Assessments of the usefulness of exhaled nitric oxide (NO) in the treatment of asthma have given conflicting results. It is not always obvious if atopic status has been tested in these evaluations.

The aim of the study is to use extended NO analysis to characterize subjects from a random sample populations with focus on rhinitis and asthma.

Data were extracted from the European Community Respiratory Health Survey II. A subgroup from the Uppsala site that had had their NO measured at multiple flow rates was included (n = 284). The nonlinear model for NO parameters was used. Atopy was defined as having a titre against at least one of the tested allergens ≥0·35 kU l(-1) . Bronchial responsiveness was assessed by methacholine challenge.

Subjects with non-atopic rhinitis or non-atopic asthma could not be separated from healthy subjects regarding NO parameters. There was a gradual increase with atopy in airway diffusion rate (D(aw) NO); healthy subject 8·0 (7·3, 8·8), healthy atopic 8·8 (6·7, 11·5), atopic rhinitis 10·6 (9·0, 12·4) and atopic asthma 11·2 (9·9, 28·3) ml s(-1) [geometrical mean (CI(95%) )]. There was a correlation between bronchial responsiveness and D(aw) NO in atopic rhinitis (r = -0·41, P<0·01), and bronchial responsiveness and airway wall content of NO (C(aw) NO) in atopic asthma (r = -0·56, P<0·001).

It is of importance to characterize atopic status when evaluating the association between NO and asthma. Our results indicate that the use of extended NO analysis, with particular attention to D(aw) NO and C(aw) NO, may be useful in monitoring treatment for rhinitis and asthma.