For omalizumab, the ATS/ERS guidelines recommend (conditionally and with a low quality of evidence) using a FeNO cutoff of ≥19.5 ppb to identify adolescents and adults with allergic SA who could be more likely to benefit from anti-IgE treatment (68), based on a subgroup analysis that showed a reduction of the exacerbation rate, a longer time to first asthma exacerbation and a larger improvement of mean QLQ in the ≥19.5 ppb subgroup (69). The gene discussed is IGHE; the disease is asthma.