Combined use of serum ferritin and KL-6 levels as biomarkers for predicting COVID-19 severity

Objectives: To assess the value of serum ferritin and Krebs von den Lungen-6 (KL-6) levels for predicting severe COVID-19 (death or requirement for invasive mechanical ventilation [IMV]/high-flow oxygen). Methods: Data were analyzed on 2495 patients with COVID-19 from February 2020 to November 2022 using data from a nationwide COVID-19 database. Results: Patients with high KL-6 and low ferritin levels were older with more comorbidities and higher mortality rates, whereas those with high ferritin and low KL-6 levels were younger, predominantly male, and more likely to need IMV. A high level of both markers was strongly associated with critical outcomes (adjusted odds ratio: 13.6, 95% confidence interval: 8.58–21.5). The combination of both markers had higher predictive value than either marker alone (area under the curve: 0.709, 0.745, and 0.781 for KL-6, ferritin, and KL-6 + ferritin, respectively). Conclusions: The combination of both markers accurately predicted COVID-19 severity.