Contribution of Exhaled Nitric Oxide Measurements to Abbreviated Bronchial Challenge Test Protocols

The bronchial challenge test is commonly used to diagnose asthma but it is a tedious, time-consuming procedure. Although in recent years, several shortened methods have been proposed, it has been shown that they can give rise to exaggerated bronchoconstriction. The aims of the present study were a) to determine the frequency of exaggerated bronchoconstriction in patients with asthma following the application of a shortened bronchial challenge test, and b) to determine if the fraction of exhaled nitric oxide (FE NO) can be used to predict the onset of exaggerated bronchoconstriction. We performed a prospective study of 210 patients with asthma in whom FE NO levels were measured in accordance with the abbreviated protocol recommended by the European Respiratory Society (ERS). Exaggerated bronchoconstriction was defined as a decrease of more than 20% in forced expiratory volume in 1 second after the first challenge, after a skipped dose, or after administration of saline. A receiver operating characteristic (ROC) curve was generated to determine the best FE NO cutoff value for predicting exaggerated bronchoconstriction. The pretest probability of developing exaggerated bronchoconstriction was also calculated using Bayes' theorem. The frequency of exaggerated bronchoconstriction in our series was 30%. Patients who developed exaggerated bronchoconstriction had significantly higher FE NO levels than those who did not (32.6 vs 16.2 parts per billion [ppb]). The chosen FE NO cutoff of 19.5 ppb had a sensitivity of 80%, a specificity of 77%, and a negative predictive value of 88%. The area under the ROC curve was 0.83 (95% confidence interval, 0.77–0.89). The abbreviated bronchial challenge test recommended by the ERS led to exaggerated bronchoconstriction in 30% of the patients studied. FE NO measurements could possibly be used to identify patients at increased risk of exaggerated bronchoconstriction. The shortened challenge test can be performed safely in individuals with a FE NO of