Study On Clinical Characteristics, Laboratory Examinations, Image Features And Pulmonary Function Tests In Patients With Rheumatoid Arthritis-associated Interstitial Lung Disease

Objective:To analyze the clinical characteristics, laboratory examinations, image features andpulmonary function tests （PFTs） and arterial blood gas analysis of rheumatoid arthritis （RA）associated-interstitial lung disease （ILD） patients.Methods:A total of771patients with RA were retrospectively reviewed in department ofRheumatology and Immunology of China-Japan Union Hospital of Jilin University fromJanuary2010to January2013. There were53patients diagnosed with RA-ILD among them.We collected the duration, age, sex, smoke, infection, fever, cough, dyspea, moist crackles,swelling joint numbers, tender joint numbers, white blood cell count （WBC）, hemoglobinlevel （Hb）, platelet count （PLT）, mean platelet volume （MPV）, lactate dehydrogenase level（LDH）, serum albumin concentration （ALB）, serum globulin concentration （GLB）,erythrocyte sedimentation rate level （ESR）, C-reactive protein concentration （CRP）, immuneglobulin concentration （IgG, IgA, IgM）, Complement levels （C₃, C₄）, the level of rheumatoidfactors （RF-IgG, RF-IgA, RF-IgM）, the level of anti-cyclic citrullinated peptide antibody（anti-CCP antibody）, image features （honeycomb shade, ground-glass opacity, reticularopacity）. And we calculated the disease activity score of28joints [DAS28（CRP）, DAS28（ESR）], simplified disease activity index （S-DAI）, clinical disease activity index （C-DAI）.45patients conducted arterial blood gas analysis and PFTs. We collected hydrogen ionconcentration （pH）, oxygen partial pressure （PaO2）, partial pressure of carbon dioxide（PaCO2）,forced expiratory volume in the first second （FEV₁）, FEV1amount percentage ofpredicted value （FEV1%）, forced vital capacity （FVC）, forced expiratory volume in the firstsecond to forced vital capacity ratio （FEV1/FVC%）, forced expiratory flow from25%to75%of FVC (FEF_25%～75%/MMEF), forced expiratory flow at75%of FVC (FEF_75%), forcedexpiratory flow at75%of FVC (FEF_50%), forced expiratory flow at75%of FVC (FEF_25%),peak expiratory flow （PEF）, residual volume （RV）, functional residual capacity （FRC）, totallung capacity （TLC）, ratio of residual volume to total lung capacity （RV/TLC）, ratio offunction residual capacity to total lung capacity （FRC/TLC）, maximal voluntary ventilation （MVV）, diffusion capacity for carbon monoxide of the lung （D_LCO）, D_LCO amountpercentage of predicted value （D_LCO%）, carbon monoxide diffusing capacity per liter ofalveolar （D_LCO/VA） and D_LCO amount percentage of predicted value （D_LCO/VA%）,potential of hydrogen, oxygen partial pressure, partial pressure of carbon dioxide, andcalculated alveolar-arterial differences for oxygen [P（A-a）O₂]. And then we conducted thecorrelation analyses of PFTs and P（A-a）O₂among these patients. The53RA-ILD patientswere divided into groups by anti-cyclic citrullinated peptide （anti-CCP） antibody （group A,negative; group B, postive）, and by age （group C, age＜60years old; group D, age≥60yearsold）. Then we comparatively analyzed the clinical characteristics, laboratory examinations,image features, PFTs, arterial blood gas analysis and P（A-a）O₂between the two groups.Results:1. The incidence of RA-ILD was6.87%（53/771） in RA patients. The incidence ofRA-ILD was6.85%（10/146） in the male RA patients, but6.88%（43/625） in female. Therewas no significant of the incidence of RA-ILD between male and female （P＞0.05）.2. TLC was negatively correlated with the level of LDH （P＜0.05）. WBC count wasnegatively correlated with FVC, FEV1, FEF25～75%and FEF50%（P＜0.05）. And it waspositively correlated with FRC/TLC （P＜0.05）. D_LCO, D_LCO%, D_LCO/VA and D_LCO/VA%were positively correlated with the level of anti-CCP antibody （P＜0.05）. There were nocorrelations between laboratory examinations with the items of PFTs （P＞0.05）.3. Serum ALB concentration was positively correlated with P（A-a）O₂（P＜0.05）, but CRPconcentration was negatively correlated with P（A-a）O₂（P＜0.05）. No other correlationscould been found between laboratory examinations with P（A-a）O₂.4. The incidence of RA-ILD was8.33%（18/192） in group A, but6.39%in group B. Therewas no significant difference between the two groups （P＞0.05）. D_LCO was no significantdifference between group A and group B （P＞0.05）, but D_LCO%, D_LCO/VA andD_LCO/VA%were significantly higher in group B than group A （P＜0.05）. There were nosignificant difference of other items of PFTs between group A and group B （P＞0.05）.5.①The incidence of RA-ILD was13.57%（27/199） in the older RA patients,significantly higher than5.07%（26/572） in non-older ones （P＜0.01）.②The duration of RAor ILD, the number of swelling joint, the number of tender joints, the incidence of fever,cough, dyspnea, smoking, infection and moist crackles were not statistically significant between group C and group D （P＞0.05）.③All of the laboratory examinations were notstatistically significant between group C and group D （P＞0.05）.④There were nosignificant differences between group C and group D （P＞0.05）, according to the imagechanges, such as honeycomb shade, ground-glass opacity, reticular opacity.⑤Thepulmonary function tests （PFTs） were lower in group D than group C （P＜0.05）, includingFEV1, FVC, FEF25～75%, FEF50%and FEF75%. Restrictive ventilation function abnormalityand the small airway dysfunction are more significant in group D than group C. RV, FRC,TLC, RV/TLC, FRC/TLC, D_LCO, D_LCO/VA, FEV1%and D_LCO%were no significantdifferences between the two groups （P＞0.05）.Conclusions:1. High LDH level could predict the impaired TLC of lung function. WBC is one ofpredictors of the pulmonary function damage and small airway dysfunction.2. Serum ALB concentration and the level of CRP are associated with the lung injury.ALB concentration decrease or CRP concentration increase could imply the level of lunginjury.3. The level of Anti-CCP antibody is associated with the pulmonary diffusion function,and it could be a new predictor of the pulmonary diffusion function damage. The mechanismof the pulmonary diffusion function damage result from anti-CCP antibody need furtherresearch.4. The incidence of RA-ILD in elderly RA patients is higher than non-elderly RA patients.Physicians should pay attention to diagnose RA-ILD by PFTs and lung HRCT in elderly RApatients.5. The restrictive ventilation function abnormality and the small airway dysfunction areperformance more serious in elderly RA-ILD patients. We should improve the pulmonaryfunction of the elderly patients with RA-ILD as early as possible and prevent infection inthese patients.