Table 1

Comparison of GOLD spirometry criteria versus the standard residual (z-score) ranges

SeverityPercentage predictedSeverityStandard residual/
z-score
NormalFEV1/FVC>0.7
FEV1>80%
Normal±1.645
Mild COPDFEV1/FVC<0.7
FEV1 80%
Mild±1.645–2.500
Moderate COPDFEV1/FVC<0.7
50%<FEV1<80%
Moderate±2.510–3.500
Severe COPDFEV1/FVC<0.7
30%<FEV1<50%
Severe± >3.500
Very severe COPDFEV1/FVC<0.7
FEV1<30%