Nevertheless, where periostin has been detected in induced sputum or exhaled breath condensate (EBC) there does seem to be an association with type-2 driven asthma as sputum periostin levels have been shown to correlate with airway eosinophils and/or to be elevated in patients with eosinophil-dominant asthma [8, 9, 23, 24]. This evidence concerns the gene POSTN and asthma.