Figure 3

Percentiles of methacholine slope as a function of pretest level of FEV ₁ (among persons of reference sample aged 40 years). This figure shows the percentiles of methacholine slope as a function of pretest level of FEV₁ (among persons of reference sample aged 40 years). The horizontal line defines the threshold between "hyperreactive" and "normal" subjects as defined by a 20% fall of FEV₁ from the baseline value before or at the maximal methacholine dose. The scale of pretest level of FEV₁ extends from below the 1 st percentile to above the 99 th percentile of pretest level of FEV₁ in our reference sample.