Prognostic roles of KL-6 in disease severity and lung injury in COVID-19 patients: A longitudinal retrospective analysis

J Med Virol. 2021 Apr;93(4):2505-2512. doi: 10.1002/jmv.26793. Epub 2021 Jan 22.


To investigate the dynamic changes of Krebs von den Lungen-6 (KL-6) among patients with coronavirus disease 2019 (COVID-19) and the role of KL-6 as a noninvasive biomarker for predicting long-term lung injury, the clinical information and laboratory tests of 166 COVID-19 patients were collected, and a correlation analysis between KL-6 and other parameters was conducted. There were 17 (10.2%, 17/166) severe/critical and 149 (89.8%, 149/166) mild COVID-19 patients in our cohort. Serum KL-6 was significantly higher in severe/critical COVID-19 patients than in mild patients (median 898.0 vs. 451.2 U/ml, p < .001). KL-6 was next confirmed to be a sensitive and specific biomarker for distinguishing mild and severe/critical patients and correlate to computed tomography lung lesions areas. Serum KL-6 concentration during the follow-up period (>100 days postonset) was well correlated to those concentrations within 10 days postonset (Pearson r = .867, p < .001), indicating the prognostic value of KL-6 levels in predicting lung injury after discharge. Finally, elevated KL-6 was found to be significantly correlated to coagulation disorders, and T cells subsets dysfunctions. In summary, serum KL-6 is a biomarker for assessing COVID-19 severity and predicting the prognosis of lung injury of discharged patients.

Keywords: COVID-19; KL-6; lung injury; prognosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Biomarkers / blood
  • COVID-19 / blood*
  • COVID-19 / diagnostic imaging
  • Female
  • Humans
  • Lung / diagnostic imaging
  • Lung / physiopathology
  • Lung Injury / blood*
  • Lung Injury / diagnostic imaging
  • Lung Injury / physiopathology
  • Male
  • Middle Aged
  • Mucin-1 / blood*
  • Prognosis
  • Retrospective Studies
  • SARS-CoV-2 / isolation & purification
  • Severity of Illness Index
  • Tomography, X-Ray Computed / methods


  • Biomarkers
  • MUC1 protein, human
  • Mucin-1