Li Zuo,1,* Wenhui Zhang,2,* Ying Wang,3 Xin Qi1 

1Department of Pulmonary and Critical Care Medicine, China Aerospace Science & Industry Corporation 731 Hospital, Beijing, 100074, People’s Republic of China; 2General Practice Clinic, Sijiqing Town Community Health Service Center of Haidian District, Beijing, 100097, People’s Republic of China; 3Department of Pharmacy, Wangtai Branch of Jincheng General Hospital, Jincheng, 048006, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xin Qi, Department of pulmonary and critical care medicine, China Aerospace Science & Industry Corporation 731 Hospital, No. 3, Zhen Gang Nan Li, Feng Tai District, Beijing, 100074, People’s Republic of China, Email xinqixq015@163.com

Objective: To explore serum KL-6 level and investigate its diagnostic value in interstitial lung diseases (ILDs).
Methods: Serum KL-6 level was measured using the chemiluminescent enzyme immunoassay. Statistical analysis was performed for determining the KL-6 concentration of each group.
Results: KL-6 level (U/mL) in the ILD group was 1388.321 ± 1943.116, which was higher than that in the control group, showing a significant statistical difference. ROC curve analysis based on the receiver operating characteristic curve showed the optimal cut-off value of 402.5U/mL, sensitivity of 77.4%, specificity of 93.4%, and accuracy of 89.4%; through Chi-square test with the two groups, the positive rate of KL-6 in patients with ILD was proved to be significantly higher than that in the control group. KL-6 level was 1063.00± 504.757 in the idiopathic pulmonary fibrosis (IPF) group, 1346.892 ± 1827.252 in the connective tissue disease-associated interstitial lung disease (CTD-ILD) group, 467.889± 288.859 in the organizing pneumonia (OP) group, 8252.333± 6050.625 in the pulmonary alveolar proteinosis (PAP) group, and 359.200± 392.707 in the sarcoidosis group. The rank sum test showed that the differences were statistically significant. KL-6 level was the lowest in the sarcoidosis group, followed by that in the OP group.
Conclusion: Serum KL-6 level was confirmed to be highly sensitive, specific, and accurate in the diagnosis of ILD. Subgroup analysis showed that the KL-6 level was the lowest in the sarcoidosis group, followed by that in the OP group.

Keywords: ILD, KL-6, diagnostic value, subgroup analysis