The serum KL‐6 levels in untreated idiopathic pulmonary fibrosis can naturally decline in association with disease progression

摘要

Abstract Background Serum KL‐6 is known to be a useful biomarker for the diagnosis and assessment of the disease activity in idiopathic pulmonary fibrosis (IPF). However, some patients with untreated IPF present with a serial decline in their serum KL‐6 levels, despite showing clinical progression. Objectives The aim of the present study was to evaluate the association between the time course of the serum KL‐6 levels and the clinical course of patients with untreated IPF. Methods We conducted a retrospective study of 59 patients who met the diagnostic criteria for IPF, who regularly underwent laboratory tests, including the measurement of KL‐6 and pulmonary function tests, and who were untreated during the follow‐up period. Results The rates of decline in comparison to the baseline FVC values were comparable between survivors ( n ?=?30) and non‐survivors ( n ?=?29); however, the rates of change in comparison to the baseline KL‐6 levels were heterogeneous in all subjects, and the KL‐6 levels of the non‐survivors were observed to decline significantly more frequently in comparison to the survivors ( P ?=?.001). Patients with a higher breathlessness scale, lower pulmonary functions and higher levels of baseline KL‐6 were predisposed to demonstrate a decline in the serum KL‐6 levels during the untreated period. Conclusions A reduction in the serum KL‐6 levels of patients with untreated IPF may not mean that the disease activity has subsided. Serum KL‐6 levels can naturally decline in association with disease progression.