Refining mild asthma phenotyping with FeNO: a population-based evaluation.

The utility of fractional exhaled nitric oxide (FeNO) was evaluated alongside blood eosinophils in phenotyping mild asthma. Inclusion of FeNO improved classification accuracy and calibration in an adapted ISAR-based model; however, its predictive improvement was modest and its susceptibility to transient elevations suggests limited added value for routine clinical classification. Simplified algorithms may offer more accurate phenotyping in population-based settings with real-world constraints.