Utility of fractional exhaled nitric oxide suppression as a prediction tool for progression to biologic therapy

Rationale: The utility of fractional exhaled nitric oxide (F-ENO) suppression (FeNOSuppT) to identify non-adherence to inhaled corticosteroid (ICS) treatment has previously been reported, but whether it can predict clinical outcome remains unclear. Objectives: We examined the utility of FeNOSuppT in prediction of progression to biologic agents or discharge from specialist care. Methods: FeNOSuppT was measured at home using remote monitoring technology of inhaler use alongside daily F-ENO measurement over 7 days. Long-term clinical outcomes in terms of progression to biologic agent or discharge from specialist care were compared for non-suppressors and suppressors. Measurements and main results: Of the 162 subjects, 135 successfully completed the test with 81 (60%) positive F-ENO suppression tests. Subjects with a negative FeNOSuppT were more likely to proceed to biologic therapy (39 of 54 patients, 72%) compared to those with a positive FeNOSuppT (35 of 81 patients, 43%, p=0.001). In subjects with a positive FeNOSuppT, predictors of progression to biologic therapy included higher dose of maintenance steroid at initial assessment and prior intensive care unit admission. These subjects had a significant rise in F-ENO between post-suppression test and follow-up (median, 33 (IQR 25-55) versus 71 (IQR 24-114); p=0.009), which was not explained by altered corticosteroid dose. Conclusions: A negative FeNOSuppT correlates with progression to biologic therapy. A positive FeNOSuppT, with subsequent maintenance of "optimised" F-ENO, predicts a subgroup of patients in whom asthma control is preserved with adherence to high-dose ICS/long-acting beta 2 agonist and who can be discharged from specialist care.