Fig. 1.

Bars represent the number of patients categorized according to presence or absence of small airway dysfunction (SAD) on the ordinate axis by means of FEF+ indicator (upper and middle panels) and R5-R20+ indicator (lower panel) and in abscissa axis by means of R5-R20+ (upper panel) and FEV₃/FEV₆+ indicators (middle and lower panels). FEF+ was defined as the presence of at least two of three forced expiratory flows, i.e., FEF_25-75, FEF₅₀, and FEF₇₅, less than 65% of predicted values. FEV₃/FEV₆+ was defined as the presence of a FEV₃/FEV₆ value less than the lower limit of normal was defined. A conservative upper limit of normal for R5–R20 was chosen at 0.070 kPa·s·L⁻¹ and was defined as R5-R20+. The interrater agreement between FEF+ and R5-R20+ was slight (κ = 0.20; upper panel), between FEF+ and FEV₃/FEV₆+ was moderate (κ = 0.49; middle panel), and between R5-R20+ and FEV₃/FEV₆+ was slight (κ = 0.07; lower panel).