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SAN DIEGO – Devices that can detect levels of fractionated exhaled of nitric oxide (FeNO) can help clinicians determine if a patients with unexplained cough needs treatment with inhaled corticosteroids, researchers suggested here.

Patients who had a FeNO level greater than 50 ppb were more than twice as likely to improve on steroids treatment than patients who had lower levels of FeNO (P=0.046), said Victoria Carter, research operations director for the Singapore-based Observation and Pragmatic Research Institute.

For every 10 ppb increase in FeNO, the researchers calculated an odds ratio of 1.17 that steroids would bring improvement (95%CI 1.02-1.34; P=0.026), she told MedPage Today at her at the annual American Thoracic Society international conference.

"FeNO was associated with response to inhaled corticosteroids in terms of cough in patients with non-specific respiratory symptoms. FeNO measurement could provide a simple non-invasive diagnostic tool to support treatment for these patients."

She said the authors suggested that the improvement seen is clinically meaningful: "Normally the device used in this study measures FeNO in asthma patients, but this was a study to determine if the device and FeNO measurements can help non-specific respiratory symptoms. A lot of people present in clinical practice with cough and it is sometimes difficult for the clinicians to decide how to treat it. We found that this device is a useful tool to determine if medication is the right answer for them or not."

Carter said that if a person with non-specific cough symptoms has his or her FeNO measured, doctors can determine if there is inflammation present and if inflammation is present, the doctor could then prescribe inhaled corticosteroids if appropriate. If the FeNO is low, then something else such as cough syrup could be prescribed.

The researchers found that among patients treated with steroids, improvement (defined as a 20 mm decrease in the visual analog scale) was observed in 60 patients, while maintenance or deterioration was seen in 77 patients.

Patients were a median 48 years old, and about 45% were men. The mean visual analog scale cough severity was 41 at baseline, and the mean FeNO score at baseline was about 37 ppb. The study assessed a subset of patients who presented with cough symptoms, Carter said.

Asked for his opinion, John Mastronarde, MD, director of the Asthma Center at the Oregon Clinic at Providence Portland Medical Center, who was not involved with the study, told MedPage Today that he finds the use of the FeNO devices to be helpful in determining treatment of patients with cough, but use of the devices remains controversial: "The short answer is 'yes, it can be helpful,' but there are a lot of caveats. It is not 100% clear what the best cutoff values are. There are also things that can influence FeNO measurements -- for example, allergies can make the reading higher, and cigarette smoking can make the reading go down.

"FeNO is not an absolute test, but I think that in the right setting it has some value. It can help you with the diagnosis of asthma. In some folks, the main value is that if the value is really high, the person should respond to inhaled corticosteroids."

Mastronarde said he uses the devices in his own practice using guideline cutoffs to make treatment decisions. "I find it helpful in initial diagnosis for some people for whom it is unclear if they have asthma and/or something else. Sometimes it helps you figure out: Is this their asthma causing symptoms or is this a cold or sinuses that is causing symptoms. I think FeNO has gotten some renewed interest because British government guidelines now include FeNO as part of the diagnostic workup -- prompted, he said, by studies that indicated that clinician-diagnosed asthma was incorrect in about one-third of cases when a full assessment was completed.

"Chronic cough is one of those tough things – several things can cause it, and asthma is one of them -- but making sure the diagnosis is accurate is getting more attention."

Carter et al noted in the study that further research is needed to establish cut-points for recommendation.