A serological biomarker in connective tissue disease-associated interstitial lung disease: Krebs von den lungen-6 / 中华风湿病学杂志

ABSTRACT

Objective To evaluate the serum Krebs von den Lungen (KL)-6 for the diagnosis of interstitial lung disease (ILD) associated with connective tissue diseases (CTD) and its lung-CT subtypes.Methods Seventy-five CTD patients were employed for this study,44 CTD with ILD and 31 ILD without ILD.The 44 CTD patients with ILD were further divided into different subgroups based on lung-CT imaging and clinical indexes.The enzyme-linked immune sorbent assay (ELISA) was used to measure the serum KL-6 level.For those data that was abnormally distributed,the differences between groups was compared with independent samples nonparametric tests.Results The level of serum KL-6 in the CTD with ILD was significantly higher than that without ILD [(1 118±877) U/ml vs (253±144) U/ml] (Z=-6.047,P＜0.01).By using a criterion of 500 U/ml,our data suggested that the serum KL-6 level was useful for the ILD-CTD diagnosis;the sensitivity,specificity,positive and negative predictive values were 72.7％,87.1％,88.9％ and 69.2％,respectively.The serum KL-6 level,however,showed no statistical differences between ILD subtypes,i.e.,usual interstitial pneumonia (UIP),nonspecific interstitial pneumonia (NSIP) and indeterminate [(1 104±843) U/ml,(1 242±1 039) U/ml,(815±400) U/ml,respectively] (x2=0.35,P=0.84).Our data further showed that the KL-6 level was significantly higher in CTD-ILD patients with intensive lung lesions than those with limited lung lesions [(1 910±918) U/ml vs (459±268) U/ml] (Z=-4.364,P＜0.01).In addition,the KL-6 level was significantly higher in active ILDs than in inactive ILDs[(1 478±917) U/ml vs (598±475) U/ml] (Z=-3.915,P＜0.01).Conclusion The serum KL-6 is a valuable biomarker for CTD-ILD diagnosis and even for the assessment of the extent and activity of lung damage.