Risk Factors And Clinical Characteristics Of Rheumatoid Arthritis-Associated Interstitial Lung Disease

Background and objectivesRheumatoid arthritis(RA)is a chronic,systemic autoimmune disease mainly characterized by erosive,symmetrical polyarthritis.Its etiology and pathogenesis are unknown.The prevalence of RA is about 0.5%-1%.And the clinical manifestations of patients with RA are mainly swelling and pain of joints.However,approximately 40%of RA patients can be involved in extra-articular organs,of which RA involving respiratory system leads to rheumatoid arthritis-associated interstitial lung disease(RA-ILD)is very common.The exact incidence and prevalence of RA-ILD are not clear.It is estimated that about 10%-40%of patients with RA can develop RA-ILD.In addition to cardiovascular diseases,RA-ILD is the most important cause of death in RA patients,and its mortality is on the rise.The pathogenesis and risk factors of RA-ILD are unclear.And the clinical manifestations of patients with RA-ILD are varied,and its symptoms and signs are nonspecific.It mainly relies on pulmonary function tests and chest high-resolution CT for the diagnosis,and surgical lung biopsy is feasible for patients with difficulty in diagnosis.At present,there are no ideal biomarkers for early diagnosis,high-risk population identification,monitoring treatment response and prognosis prediction of RA-ILD.In addition,due to the lack of high-quality evidence,the treatment of RA-ILD is mainly based on empirical judgment.Unfortunately,most of the treatment drugs have no definite effect.Overall,RA-ILD had a poor prognosis,with median survival of only 3-10 years after diagnosis.In summary,RA-ILD is a common and serious complication of RA patients with poor prognosis,which greatly increases the disease burden of RA.However,the current understanding of RA-ILD is limited,and the early diagnosis,disease assessment and accurate treatment of RA-ILD are still facing great challenges,which may cause the delay of treatment to a certain extent and is not conducive to the improvement of prognosis.In view of this,this study aims to retrospectively analyze clinical data of patients with RA-ILD and summarize its clinical characteristics,and explore the possible risk factors,in order to help clinicians improve their understanding of RA-ILD and provide some references for further research in the future.Methods86 patients with RA-ILD who were hospitalized in the First Affiliated Hospital of Zhengzhou University from June 1,2018 to May 31,2019 were selected as the study subjects.Meanwhile,86 RA patients without ILD who were hospitalized in the same period were randomly selected as the control group.Then,we retrospectively analyzed the sex distribution,age,age at RA onset,duration of RA,clinical symptoms and signs,smoking history,laboratory tests,pulmonary function tests,chest HRCT,therapeutic drugs and other clinical data of the two groups.And the multivariate logistic regression model was used to analyze the risk factors of RA-ILD.ResultsIn this study,a total of 172 patients were included.There were 86 cases in the RA-ILD group and control group respectively.The percentage of male patients in the RA-ILD group was 34.88%,and the average age of patients was 59.60±9.68 years old.The average age at RA onset was 52.13±11.86 years old.The average course of RA was 7.46±7.40 years.The percentage of the smoking patients was 24.42%.Compared with the control group,in the RA-ILD group,the male composition ratio was higher,the age and age at RA onset were older,and the course of RA was longer,P<0.05,the differences were statistically significant.There was no statistically significant difference in the smoking history between the two groups of patients(P=0.076).In the RA-ILD group,59.30%of patients had cough symptoms(90.20%were dry cough),46.51%of patients suffered from dyspnea after activity.And 37.21%of patients had symptoms of cough and dyspnea after activity.However,patients with chest pain,fatigue,and other symptoms accounted for 9.30%.Moreover,22.09%of patients had no clinical symptoms.In terms of the signs,10.47%of patients in the RA-ILD group had Velcro rales signs,and only 3.49%of patients had clubbing digits.The average RF detection concentration of patients in the RA-ILD group was 657.81(895.03)IU/mL,the average anti-CCP concentration was 416.24±396.66U/mL,and the average concentrations of CRP and ESR were 57.70±55.80mg/L and 75.99±31.46mm/1h,respectively.The results were all higher than the control group,P<0.05,the differences were statistically significant.However,there were no statistically significant differences between the two groups of patients in terms of the positive rates of RF and anti-CCP(67.44%vs.62.79%,P=0.405;87.21%vs.80.23%,P=0.524).The average percentage of the measured value to estimated value of TLC in the RA-ILD group was 89.09±15.64(%)on average,the result was lower than the control group(100.02±16.26),P<0.05,the difference was statistically significant.However,for the comparison of VC,FEV1 and FEV1/FVC between the two groups of patients,there were no statistically significant differences.In the RA-ILD group,61.63%of patients revealed restricted ventilatory defect with decreased diffusing capacity of the lung for carbon monoxide in the pulmonary function tests,17.44%of patients showed simple decreased carbon monoxide diffusion capacity,8.14%of patients had simple restricted ventilatory defect,and 12.79%of patients had normal pulmonary function.In terms of the findings of chest HRCT imaging,in the RA-ILD group,58.14%of patients had reticular pattern(predominantly bilateral and basal distribution),and 37.21%of patients had ground-glass opacity(mainly bilateral distribution),32.56%of patients had ground-glass opacity with reticular pattern.However,only 20.93%of patients had honeycombing,17.44%of patients had nodular pattern,and 1.16%of patients had consolidation.The findings of HRCT of patients with RA-ILD were comprehensively analyzed,among them,the percentage of UIP pattern was 20.93%,the percentage of NSIP pattern was 37.21%.In the RA-ILD group,the usage rates of Tripterygium glycosides and glucocorticoids were 13.95%and 41.86%respectively.The results were higher than the control group(5.82%and 25.58%respectively),P<0.05,the differences were statistically significant.For the comparison of the usage rates of methotrexate,leflunomide and non-steroidal anti-inflammatory drugs(17.44%vs.22.09%,P=0.602;16.28%vs.15.12%,P=0.658;9.30%vs.6.98%,P=0.470),the differences were not statistically significant.The multivariate logistic regression analysis showed that the age(OR=2.20,95%CI=[1.04,4.65],P=0.040),age at RA onset(OR=2.55,95%CI=[1.11,5.90],P=0.028),and anti-CCP(OR=2.47,95%CI=[1.19,5.17],P=0.016)were associated with RA-ILD.Conclusions1.The most common respiratory symptom in patients with RA-ILD is dry cough.2.In patients with RA-ILD,the pulmonary function tests mainly reveal restricted ventilatory defect with decreased diffusing capacity of the lung for carbon monoxide.3.The most common chest HRCT finding in RA-ILD is predominantly bilateral and basal reticular pattern.4.The age,age at RA onset,increased level of anti-CCP may be risk factors for the development of RA-ILD.