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Abstract: By evaluating S100 calcium binding protein A9 (S100A9) and Klebs von den Lungen-6 (KL-6) expression in patients with 4 common interstitial lung diseases (ILDs), we aimed to investigate whether S100A9 or KL-6 can be of any value in the differential diagnosis of these ILDs and simultaneously signal the disease progression.We collected the data of patients diagnosed with the 4 ILDs and underwent fiber-optic bronchoscopy and BAL in the First Affiliated Hospital, China Medical University from January 2012 to December 2020. The data related to BGA, C-reactive protein, pulmonary function test, total number and fraction of cells, T lymphocyte subsets in bronchoalveolar lavage fluid (BALF), and the expression of S100A9 and KL-6 in BALF and serum were collected. We analyzed, whether S100A9 or KL-6 could serve as a biomarker for differential diagnosis between the 4 common ILDs; whether the levels of S100A9 and KL-6 correlated with each other; whether they were correlated with other clinical parameters and disease severity.This study included 98 patients, 37 patients with idiopathic pulmonary fibrosis (IPF), 12 with hypersensitivity pneumonitis, 13 with connective tissue disease-associated ILD, and 36 with sarcoidosis (SAR): stage I (18), stage II (9), stage III (5), and stage IV (4). The expression of KL-6 in BALF was significantly higher in IPF patients than other 3 groups (all P-value < .05). However, there was no significant difference in the levels of S100A9 in BALF and serum between the 4 groups (P-value > .05). The levels of S100A9 in BALF of IPF patients was positively and significantly correlated with KL-6 expression and the percentage of neutrophils in BALF (P-value < .05). Along with the stage increase of SAR patients, the level of S100A9 in BALF gradually increased, which was negatively and significantly correlated with the forced vital capacity/predicted, carbon monoxide diffusing capacity/predicted%, and PaO2 (all P-value < .05).The expression of KL-6 in BALF can be used as a biomarker to differentiate IPF from the other 3 common ILDs. While, this was not the case with expression of S100A9 in BALF and serum. However, the expression S100A9 in BALF is useful to indicate the progression of SAR. Thus, simultaneous measurement of KL-6 and S100A9 levels in BALF makes more sense in differential diagnosing of the 4 common ILDS., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Pirfenidone is the first antifibrotic drug approved for the treatment of idiopathic pulmonary fibrosis (IPF) and it is used in the treatment of other interstitial pneumonias, such as unclassifiable interstitial lung disease (ILD) and connective tissue-related ILD. This study examined the efficacy of pirfenidone in patients with IPF and fibrotic idiopathic non-specific interstitial pneumonia (f-iNSIP)., Methods: In a retrospective real-life study, 67 IPF and 24 f-iNSIP patients were enrolled and classified into a pirfenidone group and a non-antifibrotic group. The level of forced vital capacity (FVC) and diffusing capacity of lung for carbon monoxide (DLco) at baseline, 6, 12 and 24 months were recorded. The level of KL-6 in serum was detected by chemiluminescence enzyme immunoassay (CLEIA). The prognosis and safety outcomes were collected from patients., Results: In IPF patients, pirfenidone decreased the mean change of FVC and DLco, and decreased the proportion of patients with a ⩾10% decline in FVC or a ⩾15% decline in DLco compared with the non-antifibrotic group. There was no difference in the mean change of FVC and DLco between smokers and non-smokers who received pirfenidone treatment. There was an improvement in progression-free survival, defined as the time to the first occurrence of acute exacerbation or death related to pulmonary fibrosis. Moreover, the ratio of patients who experienced acute exacerbation and death related to pulmonary fibrosis was lower in the pirfenidone group. There was no change in lung function and prognosis between the pirfenidone and non-antifibrotic groups in f-iNSIP patients. The KL-6 level slightly decreased after 1 year of pirfenidone treatment but not significantly. Gastrointestinal and skin-related adverse events were most common, and four patients ceased treatment due to the side effects., Conclusions: Pirfenidone safely reduced disease progression by improving the lung function and progression-free survival in IPF patients, with acceptable side effects. The efficacy of pirfenidone on f-iNSIP was not significant, suggesting the need for further studies. The reviews of this paper are available via the supplemental material section .