MUC1 and idiopathic pulmonary fibrosis: A study of 77 patients with IPF by Ohshimo et al. demonstrated that patients who developed acute exacerbation (n = 13) had significantly higher baseline serum KL-6 levels (2528 ± 1645 U/mL vs. 1584 ± 1000 U/mL; P < 0.0001) than those without acute exacerbation, suggesting that serum KL-6 could be a predictive marker for disease progression in IPF [22].