If this is not your name, click here.
| | If this is not your name, click here. | | |
| | Contact Us | Order Now | Journals | Bookstore | Register a colleague | | |
| |  Exhaled Nitric Oxide Measurements Can Be Used to Both Diagnose and Rule Out Asthma: Presented at AAAAI By Carole VanSickle Ellis NEW ORLEANS -- March 3, 2010 -- 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.” The researchers went on to correlate higher FeNO levels with a positive methacholine test and with basal forced expiratory volume in 1 second (FEV1) and establish a cutoff point for asthma diagnosis at FeNO 39.5 ppb. The team found no correlation between PC20 (a decrease of 20% in FEV1) and FeNO levels. They also found no correlation between FeNO measurements and variables including age, sex, body mass index, smoking habits, atopy, lung function, symptoms, and medication. International guidelines specify that asthma may be diagnosed via clinical history, reversible airway obstruction, and bronchial hyperresponsiveness. Dr. Pedrosa and colleagues believe that FeNO measurements can be a helpful tool in asthma diagnosis, particularly if the patients are not able to perform methacholine test challenges. A FeNO of 39.5 ppb can also be used as a good “negative predictive value” and may be useful in ruling out asthma in addition to diagnosing it positively.
[Presentation title: The Use of Nitric Oxide in Asthma Diagnosis. Abstract 25]
|
