MedWire News: Asthma and allergy are associated with elevated fractional concentrations of nitric oxide in exhaled breath (FeNO) of children, with the highest FeNO levels found in those with both conditions, according to a study published in the journal Pediatric Pulmonology.

The Canadian researchers also found an association between eczema and elevated FeNO, leading them to suggest that FeNO may reflect allergic conditions, rather than just asthma.

Tom Kovesi from the Children’s Hospital of Eastern Ontario, and Robert Dales, of Health Canada, Ottawa, previously reported that FeNO is affected by racial origin, age, and height in healthy children. In this study, they investigated potential associations of FeNO with allergy and respiratory symptoms.

FeNO was measured in 1135 children, aged 9–12 years, who were classed as having allergies but not asthma (n=253, 22.3%), asthma but not allergies (81, 7.1%), asthma and allergies (144, 12.7%), or healthy with no asthma or allergies (657, 57.9%).

The results show that children with asthma and allergies, allergies only, or asthma only all had significantly higher FeNO than the healthy group, at means of 22.8, 18.1, and 15.8 versus 14.0 parts per billion (ppb), respectively. FeNO was not associated with respiratory symptoms in healthy children, although healthy children were significantly more likely to have abnormally high FeNO if they reported having bronchitis or pneumonia in the past year.

A total of 116 children (10.3%) had a diagnosis of eczema before the age of 2 years, and this was associated with increased FeNO. However, after accounting for factors including racial ancestry, age, and height the association was no longer significant.

FeNO is reportedly more sensitive than spirometry for measuring airway inflammation in children with asthma, and the authors suggest: “When a marked increase [in] FeNO in children with allergies is observed, careful evaluation for respiratory symptoms consistent with asthma may be warranted.”

Free abstract