Analysis Of Clinical Features And Risk Factors Of Connective Tissue Disease Associated With Interstitial Lung Disease Complicated With Pulmonary Infection

BackgroundConnective tissue disease（CTD）is a group of systemic diseases characterized by autoimmune and autoimmune-mediated organ damage.It can affect multiple systems throughout the body.The lung is one of the most frequently affected organs^[1].Interstitial lung disease（ILD）is a complication of connective tissue disease involving the lungs.It is shown as alveolitis in early stage,pulmonary fibrosis and respiratory failure in the late stage.It is common for patients with connective tissue disease-related interstitial lung disease（CTD-ILD）to have an infection,especially pulmonary infection.Clinically,this group of patients has a high incidence of pulmonary infection,which is an important factor influencing clinical outcomes and one of the most important causes of death of patients^[2].The low immune status caused by the use of corticosteroid and immunosuppressive agents in these patients is often complicated by severe infections.The clinical manifestations,imaging,and etiologic characteristics of these are different from those with common community-acquired pneumonia.Therapeutic experience has been used for diagnosis and treatment,but there are few literature studies which can guide the clinical practice,or there is insufficient evidence in evidence-based medicine.Clinicians,especially non-respiratory physicians,are lack of experience to identified infections and progression of ILD.Delay in diagnosis and treatment may lead to progression of the disease.Therefore,in addition to improving the diagnosis and treatment of connective tissue disease-related interstitial lung disease（CTD-ILD）,it is also necessary to pay attention to and prevent the occurrence of complications.To study the clinical features of CTD-ILD combined with pulmonary infection,analyze the risk factors,identify and treat early,are very important for improving the life quality of patients,and reducing mortality.ObjectivesThis study analyzed the clinical manifestations and laboratory and imaging data of patients with connective tissue disease-related interstitial lung disease,compared the clinical features of patients with or without pulmonary infection,and explored the risk factors for pulmonary infection,which may provide a theoretical basis in early identification,clinical diagnosis and treatment.MethodsTo retrospectively collect clinical data of patients with connective tissue disease complicated by interstitial lung disease who were hospitalized in the Department of Rheumatology and Immunology,Guangzhou First People’s Hospital from August 23,2012to December 30,2017.Those patients with pulmonary infection were classified as infected group,and those without pulmonary infection were classified as non-infected group.Record patient’s gender,age,duration,clinical manifestations,laboratory tests,includingWhitebloodcellcount（WBC）,Hemoglobin（HGB）,Neutrophil percentage（NEUT%）,erythrocyte sedimentation rate（ESR）,C-reactive protein（CRP）,procalcitonin（PCT）,serum albumin（ALB）,immunoglobulin（IgA,IgG,IgE）,complement（C3,C4）,blood gas analysis,high-resolution CT of the lung,treatment status and other related information.To compare the difference of infection group and non-infected group,such as general conditions,clinical manifestations,laboratory tests,high-resolution CT of the lungs,etc.To predict related risk factors of pulmonary infection by Logistic regression analysis.SPSS software was used in statistical analysis.Results（1）There were 101 patients with CTD-ILD,41 with infection and 60 with non-infection.There were significant differences in age and course of disease between two groups（P<0.05）.（2）The incidence of connective tissue disease-associated interstitial lung disease withpulmonary infection was 40.59%,of which polymyositis/dermatomyositis（60%）,systemic sclerosis（54.5%）,and overlap syndrome（38.9%）were the most commondieases.（3）Patients with connective tissue disease-associated interstitial lung disease complicatedwith pulmonary infection mostly presented with symptoms of fever,cough,sputum,chest tightness,and shortness of breath.Lung auscultation showed more dry and wetrales than non-infected patients（P<0.05）.（4）The serum leukocyte count,the percentage of neutrophils,C-reactive protein andprocalcitonin were significantly increased in the patients with pulmonary infection inconnective tissue disease-associated interstitial lung disease,and serum albuminlevels were decreased（P<0.05）.However,the hemoglobin and erythrocytesedimentation rates were not statistically different between the two groups（P>0.05）.（5）The partial pressure of arterial blood oxygen in patients with CTD-ILD withpulmonary infection was significantly lower than that in non-infected patients,andthe patients in the infected group were prone to sputum type respiratory failure.Thefrequency of using ventilator was higher than that of non-infectious patients.（6）There was no significant difference in the levels of immunoglobulins（IgA,IgG,IgE）and complement（C3,C4）between infected and non-infected groups（P>0.05）.（7）High-resolution CT scan of the lungs in CTD-ILD patients mostly showed groundglass,cord-like,grid-like,honeycomb-like changes,and some were accompanied bybronchiectasis.The difference between the two groups was statistically significant（P<0.05）.（8）The positive rate of sputum culture in patients with pulmonary infection was 21.8%.The common pathogens were Gram-negative bacilli（58.3%）,fungal infections（33.33%）,and gram-positive cocci infection（8.3%）.（9）The incidence of treatment with large dosage of corticosteroid（the daily dosage ofcorticosteroid more than 30mg）in the infection group was higher than that in thenon-infection group（P<0.05）,and the incidence of pulmonary infection was higher inteeatment with cyclophosphamide（P<0.05）.There was no significant difference inthe use of mycophenolate mofetil,methotrexate and azathioprine between the twogroups（P>0.05）.（10）Logistic regression analysis showed that older age,longer duration of disease,hypoalbuminemia,treatment with large dosageofcorticosteroid orcyclophosphamide,and bronchiectasis were independent risk factors for pulmonaryinfection in patients with CTD-ILD（P<0.05）.ConclusionsPatients with connective tissue disease-associated interstitial lung disease are easy to suffer from pulmonary infection,due to defense immunity impairment,structural abnormalities of respiratory tract and,combined with corticosteroid and immunosuppressant therapy.Severe pulmonary infection may increase the patient’s mortality.Fever,cough,expectoration,chest tightness,shortness of breath,wet rales in auscultation of lungs increase of white blood cell count,neutrophil percentage,C-reactive protein,elevation of calcitonin,and radiographic appearance of patchy exudation indicate pulmonary infections.The older age,longer duration of the disease,hypoalbuminemia,treatment with corticosteroid and cyclophosphamide,bronchiectasis are independent risk factors for pulmonary infection in patients with CTD-ILD.