| BackgroundInterstitial lung disease(ILD)is a group of heterogeneous diffuse lung diseases.The etiology of ILD is different,and its treatment plan and prognosis are also different.Autoimmune rheumatic disease-associated interstitial lung disease(ARD-ILD)is caused by autoimmune rheumatic disease(ARD)involving the lungs and is a type of ILD Common types.There are some ILD patients with clinically characteristic autoimmune manifestations,but they do not meet the diagnostic criteria of ARD.In order to uniformly name and manage such patients,in 2015,the European Respiratory Society(ERS)/American Thoracic Society(ATS)proposed a new term-"interstitial pneumonia with autoimmune features"(IPAF),and described its diagnostic criteria in detail.IPAF and ARD-ILD have many similar clinical features,such as autoimmune abnormalities,interstitial pneumonia,etc.The differential diagnosis of the two diseases is more difficult,so some ARD Patients are easily misdiagnosed as IPAF.Studies have found that IPAF may be an intermediate state between IIP and ARD.Over time,some patients with IPAF may convert to ARD.Although some studies have confirmed that the overall prognosis of IPAF is worse than ARD-ILD,but the prognosis of IPAF patients who may undergo transformation is better than the overall prognosis.Therefore,it is very important to clarify the factors affecting the transformation of IPAF into ARD.Previous studies have shown that female and autoantibodies are the factors affecting the conversion of IIP patients to ARD.But the factors affecting the conversion of IPAF to ARD are not clear.ObjectiveThe purpose of this study is to compare the clinical characteristics of IPAF and ARDILD,analyze the different factors,and provide tools for clinicians’ differential diagnosis through the establishment of models.On the other hand,to explore the influencing factors of the conversion of IPAF to ARD to enrich Clinicians’understanding of the clinical outcome of IPAF.MethodsThe patients with ICD-10 coding "J84.900"(interstitial pneumonia and interstitial lung disease)diagnosed by the Respiratory Department and Rheumatic Immunology Department of the first affiliated Hospital of Zhengzhou University from January 1,2016 to June 30,2018 were studied.According to the inclusion and exclusion criteria,115patients with IPAF and 133patients with ARD-ILD were selected and studied retrospectively.General data,clinical symptoms and signs,laboratory examination,pulmonary function examination,high resolution CT(HRCT)imaging results,treatment plan and follow-up data were collected.Statistical analysis was carried out with SPSS 25.0 and R software(Version 4.0.3).The differences between the two groups were compared by independent sample t-test,Mann-Whitney U test,chi-square test and continuously corrected chi-square test.Combined the clinical features which is statistically significant differences after FDR correction were with sex and age,we used the R(rms package)to establish the logistic regression model and draw the line diagram.We constructed a model to predict the possibility of ARD-ILD based on the differential diagnosis of patients with difficulty in IPAF and ARD-ILD.The transformation curve of IPAF to ARD was drawn by Kaplan-Meier method,and the difference between the two groups was tested by Log-rank,so we obtained the influencing factors of IPAF to ARD.Results1.The age of IPAF patients was(60.03±11.15)years old,and the age of ARD-ILD patients was(57.14±12.13)years old.The difference was not statistically significant(P>0.05).The proportion of women with IPAF is lower than that of patients with ARDILD(62.61%vs 75.94%,P=0.023).Compared with ARD-ILD patients,the proportion of clinical features in IPAF was lower,including fever(24.35%vs 45.11%,P=0.001),joint pain(28.70%vs 48.87%,P=0.001),Gottron sign(0.87%vs 6.77%,P=0.042),RF>2 times the upper limit of normal(32.17%vs 47.37%,P=0.015),anti-CCP positive(10.43%vs 21.80%,P=0.016),anti-La(SS-B)positive(2.61%vs 13.53%,P=0.002)and anti-tRNA synthetase positive(3.48%vs 12.03%,P=0.014).All differences are statistically significant(all P<0.05).2.Compared with ARD-ILD,the HRCT of IPAF had more ground glass shadow(60.87%vs 39.85%,P=0.001),consolidation(11.30%vs 3.01%,P=0.010),and less honeycomb shadow(9.57%vs 23.31%,P=0.004),mediastinal lymphadenopathy(30.43%vs 48.12%,P=0.005).OP type(13.04%vs 4.51%,P=0.016)was more,and UIP(10.43%vs 30.08%,P<0.001)was less in IPAF.The differences were statistically significant(all P<0.05).3.In this study,a differential diagnosis calculation model of IPAF and ARD-ILD was constructed,and the possibility of diagnosis of ARD-ILD was calculated according to the patient’s age,sex,fever,joint pain,ground glass shadow of HRCT and compliance with UIP.The C-index of the prediction model is 0.748.By simulating 1000 random samples for internal verification,it is concluded that the prediction model is reliable and has good testing efficiency.4.In this study,61 patients with IPAF were followed up,and it was observed that the average conversion time of ARD,in 14 patients was 12.00(4.50,23.50)months.The analysis showed that the conversion risk of female patients was 7.454 times higher than that of men(95%CI:2.510-22.140,P=0.021).The conversion risk of patients with negative ANA titer was 3.807 times higher than that of patients with positive ANA titer(95%CI:1.240-11.690,P=0.009),and the conversion risk of patients meeting the IPAF diagnostic criteria in three areas was 3.338 times higher than that of patients meeting two areas(95%CI:0.962-11.580,P=0.016).Conclusions1.Compared with patients with ARD-ILD,IPAF patients have fewer fever,joint pain,Gottron sign,and autoantibody positive.HRCT showed more ground-glass shadows and consolidation,but less cellular shadows.HRCT classification had more OP and less UIP.2.In this study,it is suggested that the calculation model composed of age,sex,fever,joint pain,ground glass shadow in HRCT and compliance with UIP can better distinguish IPAF from ARD-ILD.3.Female,negative ANA titer and three areas that meet the diagnostic criteria of IPAF are the risk factors for the conversion of IPAF to ARD. |
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