Severe acute respiratory syndrome coronavirus 2–induced direct cytopathic effects against type I and II pneumocytes mediate lung damage. Krebs von den Lungen‐6 (KL‐6) is mainly produced by damaged or regenerating alveolar type II pneumocytes. This preliminary study analyzed serum concentrations of KL‐6 in patients with coronavirus disease (COVID‐19) to verify its potential as a prognostic biomarker of severity. Twenty‐two patients (median age [interquartile range] 63 [59‐68] years, 16 males) with COVID‐19 were enrolled prospectively. Patients were divided into mild‐moderate and severe groups, according to respiratory impairment and clinical management. KL‐6 serum concentrations and lymphocyte subset were obtained. Peripheral natural killer (NK) cells/µL were significantly higher in nonsevere patients than in the severe group (P = .0449) and the best cut‐off value was 119 cells/µL. KL‐6 serum concentrations were significantly higher in severe patients than the nonsevere group (P = .0118). Receiver operating characteristic analysis distinguished severe and nonsevere patients according to KL‐6 serum levels and the best cut‐off value was 406.5 U/mL. NK cell analysis and assay of KL‐6 in serum can help identify severe COVID‐19 patients. Increased KL‐6 serum concentrations were observed in patients with severe pulmonary involvement, revealing a prognostic value and supporting the potential usefulness of KL‐6 measurement to evaluate COVID‐19 patients' prognosis.

Aim: Interstitial lung diseases (ILD) are a group of lung disorders characterized by interstitial lung thickening. Krebs von den Lungen-6 (KL-6) is a molecule that is predominantly expressed by damaged alveolar type II cells and it has been proposed as a potential biomarker of different ILD. Materials & methods: A growing literature about KL-6 has been reviewed and selected to evaluate its role in the clinical management of ILD to predict disease diagnosis, activity, prognosis and treatment response. Results: KL-6 concentrations have been evaluated in fibrotic and granulomatous lung diseases and it was demonstrated to be a biomarker of disease severity useful for clinical follow-up of ILD patients. KL-6 levels differentiated between fibrotic ILD, such as idiopathic pulmonary fibrosis and chronic hypersensitivity pneumonitis, and nonfibrotic lung disorders, including sarcoidosis and pulmonary alveolar proteinosis. Conclusion: KL-6 is predictive biomarker useful in the clinical management of ILD patients, in particular in patients with severe fibrotic lung disorders.

Background Pirfenidone and nintedanib are the sole pharmacological therapies currently approved for idiopathic pulmonary fibrosis (IPF). Limited comparison data is available in literature, despite they are both prescribed for mild-to-moderate disease. Here, we describe our almost 10 years real-life experience with antifibrotic treatment to investigate potential differences in terms of efficacy. Population and Methods We retrospectively recruited patients diagnosed with IPF and treated with pirfenidone or nintedanib at Siena Referral Center. Clinical, functional, safety and radiological data was collected at baseline and during the follow-up, according to our Center protocol. Results We retrospectively recruited 263 IPF patients (139 treated with pirfenidone and 124 with nintedanib) in the study. After 885.3 ± 559.5 days of observation, the median survival was 1224 days. No significant differences were found between pirfenidone and nintedanib in terms of survival and time to decline of forced vital capacity >10% ( p = 0.8786 and p = 0.1677, respectively). A smaller lung diffusion for carbon monoxide (DL CO ) decrease was found after 1 year of therapy with nintedanib in respect to pirfenidone ( p = 0.0167). Overall, 21 patients permanently discontinued antifibrotic treatment due to side effects (14 with pirfenidone, 7 with nintedanib); no fatal adverse events were recorded. Discussion Our results showed a similar effectiveness between pirfenidone and nintedanib in terms of mortality and functional disease progression. Both drugs confirmed their good tolerability profile and no new safety alerts were observed. Nintedanib was associated with a smaller reduction of DL CO after 1 year of follow-up compared with pirfenidone, maybe due to its antiangiogenic properties.

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Background Serum Krebs von den Lungen‐6 (sKL‐6) is an high‐molecular‐weight (200 kDa) glycoprotein predominantly expressed by damaged alveolar type II cells, and it has been proposed as a potential biomarker of different ILD. This is a prognostic biomarker for chronic hypersensitivity pneumonitis (cHP) and idiopathic pulmonary fibrosis (IPF), two diseases that share several clinical and radiological features. Little data are available on the potential role of KL‐6 in granulomatous and cystic interstitial lung diseases, including the orphan disease known as pulmonary Langerhans cell histiocytosis (PLCH). Methods For the first time, sKL‐6 concentrations were assayed and compared in 96 patients (17 PLCH, 22 IPF, 34 cHP) and 22 healthy controls. Results Serum KL‐6 concentrations were significantly higher in PLCH (599 ± 594 U/mL), IPF (1645 ± 846 U/mL) and cHP patients (1691 ± 1643 U/mL) than in healthy controls (268 U/mL) (P = .037). Area‐under‐the‐curve values of sKL‐6 were 73.4% between PLCH and healthy controls, 84.5% between IPF and PLCH and 78% between cHP and PLCH. An indirect correlation between sKL‐6 concentrations and peripheral CD1a‐positive cells was demonstrated (r = −0.82; P = .034). Conclusion Serum KL‐6 concentrations were higher in PLCH patients than in controls, reflecting the alveolar damage typical of this rare interstitial lung disease.