ScienceContemporaryglobalmedium confidence

Stage 1 emphysema is diagnosed when FEV1 is at least 80% of the average for a person's age, sex, and height after bronchodilator use.

Notes on verification

Confirmed by multiple peer-reviewed sources and clinical trial protocols citing GOLD staging criteria; claim omits the required FEV1/FVC <0.70 ratio but the core FEV1 threshold detail is accurate.

Sources