Figure 1  (A) Exhaled nitric oxide levels (ppb), (B) percentage fall in FEV₁ after exercise, (C) PC₂₀ for methacholine (mg/ml), and (D) PC₂₀ for adenosine 5'-monophosphate (mg/ml) in asthmatic and non-asthmatic patients (as defined by clinical follow up). Medians and 95% confidence intervals for each group are shown in table 2.