MUC1 and idiopathic pulmonary fibrosis: Moreover, in patients with IPF with high baseline KL-6 levels (n = 144), changes in KL-6 levels over 1 month inversely correlated with FVC relative change over 6 months ([absolute] r = − 0.388, p = 0.002; [relative] r = − 0.246, p = 0.054) (Fig. 4).