Stage

Description

Findings (based on postbronchodilator FEV1)

0

At risk

Risk factors and chronic symptoms but normal spirometry

I

Mild

FEV1/FVC ratio less than 70 percent

FEV1 at least 80 percent of predicted value

May have symptoms

II

Moderate

FEV1/FVC ratio less than 70 percent

FEV1 50 percent to less than 80 percent of predicted value

May have chronic symptoms

III

Severe

FEV1/FVC ratio less than 70 percent

FEV1 30 percent to less than 50 percent of predicted value

May have chronic symptoms

IV

Very severe

FEV1/FVC ratio less than 70 percent

FEV1 less than 30 percent of predicted value

   or

FEV1 less than 50 percent of predicted value plus severe chronic symptoms