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

Deng, Kai; Fan, Qinghong; Yang, Yanhong; Deng, Xizi; He, Ruiying; Tan, Yizhou; Lan, Yun; Deng, Xilong; Pan, Yuejun; Wang, Yaping; Guan, Yujuan; Liu, Huiyuan; Chen, Fengjuan; Mo, Xiaoneng; Tan, Xinghua; Luo, Chun; Wen, Xueliang; Liu, Ying; Liu, Jinxin; Zhang, Lieguang; Tang, Xiaoping; Hu, Fengyu; Li, Feng

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.