Association of Serum KL-6 With Mortality in Patients With Acute Respiratory Distress Syndrome (ARDS) Requiring Extracorporeal Membrane Oxygenation (ECMO): A Multicenter Retrospective Cohort Study

Identifying reliable biomarkers associated with clinical outcomes in patients with acute respiratory distress syndrome (ARDS) receiving extracorporeal membrane oxygenation (ECMO) is essential. Elevated serum Krebs von den Lungen-6 (KL-6) has been linked to increased mortality in ARDS; however, its prognostic utility in ECMO remains unclear. This multicenter retrospective cohort study analyzed adult patients with severe ARDS who received veno-venous ECMO in 24 Japanese hospitals between 2012 and 2022. Serum KL-6 was measured within 3 days before or after ECMO initiation. The primary outcome was 90 day in-hospital mortality, and the secondary outcome was successful ECMO liberation. Among 373 patients, 265 (71.0%) survived, and 108 (29.0%) died. In multivariable Cox proportional hazards models using restricted cubic splines, higher KL-6 levels were significantly associated with increased 90 day mortality (p = 0.004), whereas lower KL-6 levels were significantly associated with successful liberation from ECMO (p < 0.001). These findings suggest that serum KL-6 measured around the time of ECMO initiation is associated with mortality and liberation outcomes in patients with, supporting its potential as a biomarker of disease severity.