- Classification of airflow limitation severity base on FEV1% predicted [70] [72]. GOLD 1 (mild): FEV1 ≥ 80%; GOLD 2 (moderate): 50% ≤ FEV1 < 80%; GOLD 3 (severe): 30% ≤ FEV1 < 50%; GOLD 4 (very severe): FEV1 < 30% predicted.