American Thoracic Society guidelines support using fractional exhaled nitric oxide (Feno) measurements in patients with asthma and highlight gaps in the evidence base. Little is known about the use of Feno levels to predict asthma exacerbations among high-risk, urban, minority populations receiving usual care.
Children with persistent asthma (n = 138) were enrolled in a prospective, observational cohort study and skin tested at baseline (a wheal ≥ 3 mm indicated a positive skin-prick test). Feno levels, lung function, and asthma-related health-care use were assessed at baseline and every 3 months thereafter for 1 year. Relationships between Feno levels and health-care use in the subsequent 3 months were examined. Final models accounted for repeated outcome measures and were adjusted for age, sex, and lung function.
The mean age of the children was 11 years (range, 5-17 years), and most were male (57%), black (91%), and atopic (90%). At baseline, the median Feno level was 31.5 parts per billion (interquartile range, 16-61 ppb) and mean FEV1/FVC was 80.7% (SD, ± 9.6%). There were 237 acute asthma-related health-care visits, 105 unscheduled doctor visits, 125 ED visits, and seven hospitalizations during the follow-up period. Feno level was not a significant predictor of acute visits, ED visits, unscheduled doctor visits, or hospitalization in either unadjusted or adjusted analyses. Use of recommended cut points did not improve the predictive value of the Feno level (positive predictive value, 0.6%-32.8%) nor did application of the guideline-based algorithm to assess change over time.
Feno level may not be a clinically useful predictor of health-care use for asthma exacerbations in urban minority children with asthma.