Figure 2.

A. Categories based on the lower limit of normal [6]) and fixed 0.70 FEV₁/FVC definitions. FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; LLN: lower limit of normal Red diagonal line: LLN FEV1/FVC cutpoint (position and slope of this line will vary depending on the reference equation used and the height and age of the subject); black horizontal line: fixed FEV1/FVC cutpoint at 0.70 LLN-Fixed-: absence of obstruction according to both LLN and Fixed FEV1/FVC cutpoints (non-obstructed subjects) LLN-Fixed+: absence of obstruction according to LLN cutpoint, but presence of obstruction according to fixed cutpoint (discordant subjects) LLN+Fixed+: presence of obstruction according to both LLN and Fixed FEV1/FVC cutpoints (obstructed subjects) LLN+Fixed-: presence of obstruction according to LLN cutpoint, but absence of obstruction according to fixed cutpoint. Only two subjects were present in this category, who were excluded from further analysis (see Figure 1) B. Categories based on the lower limit of normal [6]and fixed 0.70 FEV₁/FVC definitions, and subgroups of subjects who showed a downward shift (A, B and C, n = 711) or an upward shift (D, E and F, n = 530) between categories over time. Subgroups A: no obstruction at baseline visit, obstruction according to fixed FEV1/FVC cutpoint at last available visit. B: no obstruction at baseline visit, obstruction according to both fixed and LLN FEV1/FVC cutpoints at last available visit. C: obstruction according to baseline FEV1/FVC cutpoint at first visit, obstruction according to both fixed and LLN cutpoints at last available visit. D: obstruction according to fixed and LLN FEV1/FVC cutpoints at baseline visit, obstruction according to fixed cutpoint at last available visit. E: obstruction according to fixed FEV1/FVC cutpoint at baseline visit, no obstruction at last available visit. F: obstruction according to fixed and LLN FEV1/FVC cutpoints at baseline visit, no obstruction at last available visit.