IGHE and asthma: It was shown that variation in key intermediate asthma phenotypes, such as airway responsiveness (sensitivity to inhaled methacholine), airway inflammation (level of exhaled nitric oxide), lung function (FEV1 and FVC, and the ratio between these), as well as atopy and serum total IgE, was also influenced to a large extent by genetic factors; however, with evidence of considerable genetic heterogeneity between these traits.