. 2007 Jul;62(7):638–649. doi: 10.1136/thx.2004.031005

Table 1 Classification of bronchiolitis obliterans syndrome (BOS)⁵³.

BOS 0	FEV₁ >90% of baseline and FEF_25–75 >75% of baseline
BOS 0‐p	FEV₁ 81–90% of baseline and/or FEF_25–75 ⩽75% of baseline
BOS 1	FEV₁ 66–80% of baseline
BOS 2	FEV₁ 51–65% of baseline
BOS 3	FEV₁ ⩽50% of baseline

BOS 0‐p, potential BOS stage; FEF_25–75, mid expiratory flow rate; FEV₁, forced expiratory volume in 1 s.

The mean of the two highest (not necessarily consecutive) measurements represents the baseline value with which the subsequent measurements are compared.

Table 1 Classification of bronchiolitis obliterans syndrome (BOS)53.

Table 1 Classification of bronchiolitis obliterans syndrome (BOS)⁵³.