Serum KL-6 Expression Level And Clinical Significance In Patients With Common Connective Tissue Disease Complicated With Interstitial Lung Disease

Purpose:To investigate the expression level of serum krebs von den lungen-6(KL-6)in patients with common connective tissue diseases complicated with interstitial lung disease(CTD-ILD),such as rheumatoid arthritis(RA),systemic lupus erythematosus(SLE),Sjogren’s syndrome(SS).To explore the clinical significance of detection of serum KL-6 expression in common CTD-ILD patients.Method:A total of 187 patients diagnosed with CTD admitted to the First Affiliated Hospital of Bengbu Medical College from April to November 2021 were selected as the study subjects.According to whether they met the diagnostic criteria of interstitial lung disease,they were divided into two groups:CTD-ILD group and CTD-NILD group.116 cases in CTD-ILD group,71 cases in CTD-NILD group.A total of 41 healthy subjects in our hospital were selected as healthy control group.The relevant data among the groups were analyzed and compared,including:(1)the age,sex,course of disease and serum KL-6 level of the subjects were compared.(2)The clinical manifestations,laboratory indexes and HRCT manifestations of patients in CTD-ILD group and CTD-NILD group were compared within 24 hours after admission.(3)Analysis of the correlation between serum KL-6 level and clinical manifestations,laboratory examination and lung HRCT manifestations in CTD-ILD patients.Results:1.General clinical data of enrolled patients:The mean age of patients in CTD-ILD group was 56.24±13.55 years old,with 102(87.9%)females and 14(12.1%)males.The course of disease was 3(0.5,10)years.The mean age of patients in the CTD-NILD group was 51.90±15.14 years old,with 61(85.9%)females and 10(14.1%)males.The course of disease was 5(0.5,10)years.The mean age of the healthy control group was 45.46±11.34 years old,with 22 females(53.7%)and 19 males(46.3%).2.Comparison of serum KL-6 levels between groups:Serum KL-6 levels in CTD-ILD group,CTD-NILD group and healthy control group were 251.40(75.95,517.87)U/mL,86.30(38.60,145.90)U/mL and 49.70(18.75,76.00)U/mL.The difference between the two groups was statistically significant(P<0.05).Further analysis showed that serum KL-6 levels of different diseases were higher in CTD-NILD group than in CTD-NILD group,and the difference was statistically significant(P<0.05).3.Comparison of clinical manifestations,physical signs and laboratory results between CTD-ILD group and CTD-NILD group:The incidence of cough,sputum,chest tightness and lung rales in CTD-ILD group was significantly higher than that in CTD-NILD group(P<0.05).The levels of leukocyte count,neutrophil percentage,D-dimer,C-reactive protein,carcinoembryonic antigen(CEA),carbohydrate antigen 125(CA125)and carbohydrate antigen 153(CA153)in CTD-ILD group were significantly higher than those in CTD-NILD group,while the albumin level was significantly lower than that in CTD-NILD group(P<0.05).4.Receiver Operating characteristic(ROC)curve analysis of serum KL6 in the diagnosis of CTD-ILD:The cut-off value of serum KL-6 in the diagnosis of CTD-ILD was 207.8U/mL,the area under ROC curve was 0.773,the sensitivity was 56.0%,the specificity was 98.2%,and the Yoden index was 0.542.5.Correlation analysis:Serum KL-6 was significantly higher in CTD patients with cough,sputum,chest tightness,pulmonary rales,Raynaud’s phenomenon,and myalgia than in CTD patients without the above symptoms(P<0.05).Serum KL-6 levels in CTD-ILD patients were positively correlated with CEA,CA125 and CA153(r=0.413,P<0.001;r=0.336,P=0.005;r=0.689,P<0.001).HRCT showed that a significant number of patients with CTD-ILD presented two or more imaging signs at the same time,including 73 cases of fibrous strip shadow,41 cases of mesh shadow,3 cases of honeycomb shadow,14 cases of ground glass shadow,60 cases of patchy exudation shadow,and 5 cases of thin-wall cyst shadow.According to stratified HRCT analysis,the serum KL-6 level in acute ILD group was 295.30(103.20,628.30)U/mL,and that as in chronic ILD group was 155.50(43.45,345.95)U/mL.The acute group was significantly higher than the chronic group(P=0.010).Serum KL-6 level of CTD-ILD was significantly positively correlated with the extent of ILD involvement as indicated by lung HRCT(r=0.681,P<0.05).Conclusion:1.Serum KL-6 level in CTD-ILD patients was significantly higher than that in CTD-NILD group and healthy subjects,and detection of serum KL-6 level could be used as a reference index to predict CTD-ILD.2.For CTD patients with respiratory symptoms or signs,abnormal increase of white blood cell count and neutrophil percentage,significant increase of serum D-dimer and C-reactive protein,and decrease of albumin,it is recommended to detect serum KL-6 level and combine lung imaging examination for early screening of ILD.3.Timely detection of serum KL-6 levels in CTD patients,combined with periodic lung HRCT examination,may lead to early detection of CTDILD and assessment of its severity,and timely adjustment of treatment and treatment protocols.