IL6 and idiopathic pulmonary fibrosis: Furthermore, predictive factors of disease progression are the presence of UIP pattern, high titers of anti-citrullinated cyclic peptide (ACPA) antibodies, baseline deterioration of DLCO, a %FVC decline ≥ 10% during the follow-up, and elevated serum levels of interleukin 6 (IL-6) and KL-6.