This calculates how much a person's FEV₁ improves after using a bronchodilator — the key spirometry test used to confirm an asthma diagnosis.
A positive test needs both ≥ 12% and ≥ 200 mL improvement.
Yes — partial reversibility can occur in COPD, which is why the diagnosis relies on the overall clinical picture rather than this one test alone.
An increase of at least 12% AND at least 200 mL in FEV₁ after the bronchodilator is generally considered significant, supporting asthma over fixed obstruction.
The percentage alone can exaggerate small changes in people with low baseline FEV₁, so pairing it with a 200 mL minimum keeps the result meaningful.
No — asthma is variable, so a single non-reversible test doesn't exclude it. Repeat testing or other measures may still support the diagnosis.