Clinical applications of exhaled nitric oxide for the diagnosis and management of asthma: A consensus report

Background: Patients with asthma routinely exhibit elevated levels of fractionated exhaled nitric oxide (FENO), and this observation has led to studies investigating FENO as a potential marker of airway inflammation. FENO has been shown to enhance the diagnosis of asthma, detect deterioration in control of patients with asthma, and monitor response to anti-inflammatory therapy. Objectives: The aim of this work was to determine if FENO measurement provides a noninvasive, well-tolerated, and standardized technique to monitor airway inflammation, and if it has the potential to complement standard asthma monitoring tools (eg, symptom diaries, control questionnaires, and pulmonary function testing) and to improve asthma control and patient outcomes. Methods: Thirteen experts in the diagnosis and treatment of asthma met to discuss the use of FENO in the diagnosis and management of patients with asthma. Participants were selected by Aerocrine, a medical, technical company with headquarters in Stockholm, Sweden, in consultation with their medical education partner Cadent Medical Communications located in Irving, Texas, to represent a diversity of specialists, including both clinicians and investigators, in the fields of allergy, immunology, and pulmonology. All participants were nominally compensated for their time to attend this closed scientific roundtable discussion. The meeting was supported by an educational grant from Aerocrine. This report represents the overall consensus reached by the participants on the clinical applicability of this technique. Results: Our understanding of asthma has expanded so that investigators are now focusing on inflammation in addition to airway obstruction and hyperreactivity. Whereas patient history, symptoms, and pulmonary function testing can assist in diagnosing asthma, they are not direct measures of the extent of airway inflammation. Elevated FENO levels have been shown to reflect airway inflammation and to occur together with other conventional markers used to detect inflammation. Studies have confirmed increased levels of FENO in both adults and children with asthma. In most studies, FENO was found to be elevated 2- to 3-fold compared with normal controls. There are many determinants of FENO levels, however, and factors other than inflammation must be considered when FENO measurement is used to diagnose and monitor asthma. FENO measurement alone is not sufficient for diagnosing or monitoring asthma, but it can be a valuable addition to current clinical tools. Conclusions: FENO measurement is a noninvasive and reproducible test that is a surrogate measure of airway inflammation in patients with asthma. The test has demonstrated utility in diagnosing and managing asthma and in predicting response to therapy and, therefore, may be an important tool to incorporate into clinical care.