Exhaled Nitric Oxide Measurements Can Be Used to Both Diagnose and Rule Out Asthma: Presented at AAAAI
Posted Mar 07 2010 11:15pm
Doctors have been using fractional exhaled nitric oxide (FeNO) measurements to indicate airway inflammation and aid in asthma diagnosis for some time, leading many to believe that these measurements could play a role in actually diagnosing the problem. As it turns out, this noninvasive, inflammatory marker may not only send up a red flag for a positive diagnosis but also aid in confirming a negative one, according to a study presented here at the 2010 American Academy of Allergy, Asthma & Immunology (AAAAI) Annual Meeting.
In the study, a group of 115 patients who were reporting asthma symptoms were assembled. The patients had "perennial symptoms consistent with asthma," with normal spirometry and a negative bronchodilator test. They also met medication withdrawal requirements before testing and completed an Asthma Control Test and Asthma Control Questionnaire before the research protocol began. After undergoing a methacholine challenge test following the standard 5-breath dosimeter protocol, FeNO measurements were taken with a portable device at a 50-mL/s exhalation flow rate.
Thirty-five of the 115 patients had a positive methacholine test and were diagnosed with asthma, making the prevalence of asthma in the test population 30.43%. FeNO levels in asthmatic patients averaged 58 parts per billion (ppb) (interquartile range [IQR] 36.00-112.00), whereas they averaged 29.5 ppb in patients not diagnosed with asthma (IQR 21.00-42.75; P = .0001). Maria Pedrosa, MD, University Hospital La Paz, Madrid, Spain, stated in a presentation on February 27 that these results showed that "FeNO levels are significantly higher for asthmatics…than non-asthmatics."