Spirometry: FEV1/FVC & obstruction pattern

Computes the FEV1/FVC ratio and flags an obstructive pattern, with optional bronchodilator reversibility (ATS/ERS 2022).

Evidence tier: Guideline-derived.

Formula / logic

FEV1/FVC ratio. Fixed cutoff <0.70 defines obstruction (GOLD); prefer the lower-limit-of-normal (LLN, z-score < −1.645) where reference equations are available. Bronchodilator responsiveness, classic: ΔFEV1 (or ΔFVC) ≥12% AND ≥200 mL from baseline; ATS/ERS 2022: ΔFEV1 (or ΔFVC) >10% of the predicted value.

Interpretation

A fixed 0.70 ratio over-diagnoses obstruction in older adults and under-diagnoses in young adults; use LLN-based interpretation when the reference equation is available.

Evidence & citations

  1. Stanojevic S, Kaminsky DA, Miller MR, et al. ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J. 2022;60(1):2101499. PMID 34949706
  2. Global Initiative for Chronic Obstructive Lung Disease (GOLD) report, fixed FEV1/FVC <0.70 obstruction criterion. GOLD report

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