MUC1 and idiopathic pulmonary fibrosis: However, potential criticisms of this study including the small number of a specific group of IPF patients studied, the finding that the KL-6 levels in the pretreatment period could not be used to predict outcome as well as the evidence that KL-6 concentrations are affected by certain malignancies [12,53] pose major limitations to these observations and highlight the necessity for further investigation and studies.