In the present study we compared the two analytical methods, FEIA and CLEIA, for detecting KL‐6 in serum and BAL, with the aim of further validating its diagnostic value in different ILDs, including idiopathic pulmonary fibrosis (IPF), connective tissue disease‐associated with interstitial lung disease (CTD‐ILD) and sarcoidosis. The gene discussed is MUC1; the disease is sarcoidosis.