Exhaled nitric oxide's ability to predict methacholine challenge

I read with interest the article "Evaluation of Exhaled Nitric Oxide's Ability to Predict Methacholine Challenge in Adults With Nonobstructive Spirometry" by Nickels and Lim, recently published on Annals of Allergy, Asthma, and Immunology.1 Their study, which was retrospectively conducted and selected patients who performed fractional exhaled nitric oxide (FeNO) and methacholine bronchial challenge within 2 weeks of each other, found that FeNO had a nonbrilliant ability to predict the outcome of a methacholine challenge, despite patients with positive methacholine challenge result having signficantly higher levels of FeNO.

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