FeNO interpretation (ATS 2011)

Interprets fractional exhaled nitric oxide against the ATS age-specific thresholds for eosinophilic airway inflammation / corticosteroid responsiveness.

Evidence tier: Guideline-derived.

Formula / logic

Adults/≥12 y: <25 ppb low, 25-50 intermediate, >50 high. Children <12 y: <20 ppb low, 20-35 intermediate, >35 high.

Interpretation

High FeNO supports eosinophilic airway inflammation and predicts corticosteroid responsiveness. Low FeNO does not exclude asthma (e.g. neutrophilic phenotypes, smokers, or recent steroid use lower FeNO).

Evidence & citations

  1. Dweik RA, Boggs PB, Erzurum SC, et al. An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FeNO) for clinical applications. Am J Respir Crit Care Med. 2011;184(5):602-615. PMID 21885636

Clinician decision support. Verify against the cited source. Not a substitute for clinical judgment. 100% on-device; no patient data is stored or transmitted.