Exploration and correlation analysis of changes in Krebs von den Lungen-6 levels in COVID-19 patients with different types in China.

This study aimed to determine the clinical significance of Krebs von den Lungen-6 (KL-6) in patients with COVID-19, so as to find a marker with high sensitivity, specificity and easy detection to evaluate the lung injury and inflammation of COVID-19. Sixty-three COVID-19 patients and 43 non-COVID-19 patients with similar clinical phenotypes and/or imaging findings were enrolled to test the levels of KL-6 using chemiluminescent immunoassay. In addition, the blood gas, imaging and lymphocyte factors tests were collected from all participants. The data was finally analyzed using multivariate statistical analysis. The results showed KL-6 levels in COVID-19 patients were higher than those in non-COVID-19 patients (P < 0.001). Moreover, the KL-6 levels in severe and critically severe patients were significantly upregulated compared with patients with mild and common type (P < 0.05). Meanwhile, the imaging evaluation showed a significant correlation between KL-6 and pulmonary lesion area (P < 0.05). KL-6 was also found to be significantly correlated with oxygenation index and oxygen partial pressure difference of alveolar artery (PA-aDO2) (Both P < 0.01). In conclusion, KL-6 could be an indicator to evaluate the progression of COVID-19, which is parallel to the level of lung injury and inflammation in patients. Moreover, it can also reflect the pulmonary ventilation function.