Idiopathic Pulmonary Fibrosis based on disease behavior: Workshop summary of a Japanese multicenter study

Background: Although the Fleischner Society’s white paper and the ATS/ERS/JRS/ALAT guideline for Idiopathic Pulmonary Fibrosis (IPF), 10-20% of Idiopathic Interstitial Pneumonias (IIPs) were diagnosed as unclassifiable IIPs and can be managed as IPF based on disease behaviour. Subject and Methods: To characterize such patients we collected clinical data, HRCT, and pathological slides of 25 cases with the final diagnosis of IPF {initial local diagnosis of non IPF and final IPF by disease behaviour {G1; n=17, 16 unclassifiable IIPs, 1 chronic hypersensitivity pneumonitis (CHP)} and initially definite IPF (G2; n=8)} from 10 centers. We reviewed in the IPF workshop according to the Fleischner Society criteria (2017) in August, 2018. Results: 41% (7/17) of initial non IPF were IPF (MDD) and 25% (2/8) of initial IPF were non IPF (CHP, unclassifiable). 25% (3/12) of Probable UIP (HRCT), and 67% (1/3) of Indeterminate for UIP were non IPF after MDD. Kappa statistic between the local diagnosis and MDD was 0.29. There was not significant difference of gender, age, smoking, dust exposure, %FVC, serum KL-6, SP-D, and honeycombing between G1 and G2. 100% of G1 and 88% of G2 progressed and developed more honeycombing in the last HRCT. 75% G1and 25% G2 were treated with Pirfenidone, and 53% G1 and 88% G2 were treated with Nintedanib. 63% G1 and 29% G2 developed acute exacerbation. 40% of G1 and 41% of G2 were deceased, 50% of G1 and 29% of G2 were alive with worsened disease. Discussion and Conclusion: Unclassifiable IIPs should be carefully managed by disease behaviour. Surgical lung biopsy and MDD should be conditionally required for patients with probable UIP (HRCT).