Advances in the study of biomarkers of idiopathic pulmonary fibrosis in Japan.

Idiopathic pulmonary fibrosis is an intractable disease with a median survival time of 2 to 3 years. Serum levels of Krebs von den Lungen-6 (KL-6), surfactant protein A (SP-A), and surfactant protein D (SP-D) are useful biomarkers for idiopathic pulmonary fibrosis and they are widely used in Japan. Based on clinical use in Japan, a combination of KL-6, SPA, and SP-D is useful at diagnosing interstitial lung diseases and predicting the prognoses for patients with these diseases. However, the differential diagnosis of idiopathic pulmonary fibrosis from other interstitial lung diseases is still challenging. Several other biomarkers have been identified and are being studied in Japan.