Serum KL-6 concentrations as a novel biomarker of severe COVID19.

PURPOSE: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-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 analysed serum concentrations of KL-6 in COVID19 patients to verify its potential as a prognostic biomarker of severity. MATERIALS AND METHODS: Twenty-two patients (median age (IQR) 63 (59-68) years, 16 males) with COVID19 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. RESULTS: Peripheral NK cells/�l were significantly higher in non-severe patients than in the severe group (p=0.0449) and the best cut-off value was 119 cells/�l. KL-6 serum concentrations were significantly higher in severe patients than the non-severe group (p=0.0118). ROC analysis discriminated severe and non-severe patients according KL-6 serum levels and the best cut-off value was 406.5 U/ml. CONCLUSIONS: NK cell analysis and assay of KL-6 in serum can help identify severe COVID19 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 COVID19 patients prognosis. This article is protected by copyright. All rights reserved.