FIGURE 2.

In severe asthma with documented treatment adherence to high‐dose inhaled corticosteroids (as demonstrated following a fractional exhaled nitric oxide [FeNO] suppression test), FeNO is correlated with increased induced sputum levels of airway type‐2 cytokines, chemokines and alarmins. In contrast, blood eosinophils correlate with serum IL‐5 and not with any assessed measure in sputum. These results imply that FeNO and blood eosinophils relate to different components and compartments of type‐2 inflammation, with FeNO reflecting the chemotactic pull (magnet) to the airways and blood eosinophils reflecting the systemic pool of available eosinophils (bomb). When both occur together, the risk of asthma attacks (bomb detonating) is particularly high. The biomarker profile of magnet‐driven disease is shown in the blue outlined area and bomb‐driven disease in the black outlined area overlaying a grid showing the relative risk of asthma attacks according to data from placebo arms of randomized controlled trials. Colour codes reflect the relative risk of asthma attacks: green (low risk) to red (high risk). Based on data from Couillard et al ⁵ , ⁶ ; figure reproduced from Couillard et al ¹⁰ with permission from Elsevier.