| Objective:Investigate the diagnostic value of KL-6 in RA-ILD and it’s role in evaluating lung severity and prognosis.Methods:This retrospective study included 115 patients with RA-ILD and 115 patients with gender-matched and age-matched RA in who continuously visited the hospital between January,2015 and December,2019.The baseline clinical data,laboratory parameters and imaging information were collected.Among them,80 patients with RA-ILD were divided into progressive group(n = 44)and non progressive group(n = 36)according to the presence of lung progression.Results:1.The average age of RA-ILD group was 60.02±10.59 years,the duration of rheumatoid arthritis was 4(1,10)years,there were 48 males and 67 females,17.4% of RA-ILD patients had chest tightness and shortness of breath,36.5% of RA-ILD patients had pulmonary Velcro rale,swollen joint count was 2(0,8),tender joint count was 9(2,17),the duration of morning stiffness was 1(0.5,2)hour.In RA group,The average age was 59.34±9.75 years,the duration of rheumatoid arthritis was 7(3,15)years,there were 48 males and 67 females,no(0/115)RA patients had chest tightness and shortness of breath,1.7%(2/113)patients had pulmonary Velcro rale,swollen joint count was 4(1,8),tender joint count was 10(4,17),the duration of morning stiffness was 1(0.5,1.5)hour.2.The KL-6 level,RF titer,LDH concentration,ANA positive rate,SSA positive rate and Ro52 positive rate in RA-ILD group were significantly higher than those in RA group(P<0.05),while ESR,CRP,DAS28,PLT,SM,SSB,Jo-1,Sc L-70,AKA and CCP had no significant difference between groups(P>0.05).3.The ROC analysis to assess the diagnostic abilities of the Serum KL-6 level for the diagnosis of RA-ILD showed a cut-off value of KL-6 was 278 U/ml,the sensitivity,specificity and area under the curve were 78.23%,83.48% and 0.89 respectively.4.In RA-ILD patients,KL-6 was negatively correlated with FVC(r=-0.398,P=0.003),FEV1(r=-0.292,P=0.034)and TLC(r=-0.345,P=0.012).5.KL-6 was positively correlated with HRCT score(r = 0.688,P < 0.001).6.The baseline KL-6 level in RA-ILD progression group was significantly higher than that in RA-ILD non progression group(680(502.25,881)vs 293(236,383.75),P =0.002).ROC analysis showed that the optimal cut-off value for baseline KL-6 level to determine lung progression in RA-ILD patients was 501 U/ml,the sensitivity,specificity and area under the curve were 75.00%,91.67% and 0.871.7.Multivariate logistic regression analysis showed that KL-6(OR=1.007,95% CI:1.003-1.010,P < 0.001)was an independent risk factor for lung progression in RA-ILD.Conclusions:1.In RA patients,serum KL-6 can help to distinguish ILD patients and non ILD patients,so as to improve the clinical diagnostic accuracy of RA-ILD.It is also helpful to assess the severity of the lung.2.High baseline serum KL-6 level is an independent predictor of lung progression in ra-ild patients.In clinical practice,ra-ild patients with high KL-6 level(KL-6>501U/ml)should be alert to lung progression.3.For RA-ILD,serum KL-6 is an effective and simple serological indicator.Large scale,multicenter and prospective studies are needed to verify the above findings in the future. |
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