Analysis Of The Influencing Factors For Bone Mineral Density Measured By Quantitative Computed Tomography In Patients With Rheumatoid Arthritis

Objective:To analyze the relationship between bone mineral density(BMD)and the related clinical parameters,and to explore the risk factors for osteoporosis(OP)in rheumatoid arthritis(RA),in order to find some potential independent risk factors and protective factors of secondary OP in RA patients.To improve clinicians’ early identification of patients with RA secondary OP,to provide reference for its prevention and treatment,so as to reduce the burden of disease and improve the quality of life of patients.Methods:In this study,105 RA inpatients from the Department of Rheumatology and Immunology of the First Affiliated Hospital of Kunming Medical University who met the inclusion and exclusion criteria from August 2019 to October 2020 were enrolled.BMD of Lumbar 1-3 vertebral bodies were measured by Quantitative Computed Tomography(QCT)and its mean value was analyzed.Adopt the consensus of the International Society for Clinical Bone Density(ISCD)on QCT in 2007[1].The patients were divided into normal bone mass group(BMD≥120mg/cm3),reduced bone mass group(80mg/cm3<BMD<120mg/cm3)and osteoporosis group(BMD≤80mg/cm3)according to the average BMD of lumbar 1-3 vertebrae.SPSS22.0 was used to analyze the data,and p<0.05 was considered statistically significant.Clinical parameters were compared among the three groups.The correlation between BMD and clinical parameters was analyzed.The regression model was established by multiple stepwise regression analysis.Use the forward method,first,the indexes that have the greatest influence on BMD and satisfy the judgment conditions were entered into the regression equation,and then remove the variables in the model that match the exclusion conditions from the model,repeat until no variables are introduced or excluded.A regression equation was obtained to predict the mean BMD of lumbar 1-3 vertebral bodies in patients with rheumatoid arthritis.Results:1.Among the 105 RA patients,36 patients(34.3%)were divided into normal bone mass group,35 patients(33.3%)in reduced bone mass group,and 34 patients(32.4%)in osteoporosis group.2.The age difference in the three groups of patients was statistically significant,Post-facto pairwise comparisons of the Bonferroni method for correcting significance levels found that there were statistically significant differences in age between normal bone mass group and reduced bone mass group,between normal bone mass group and osteoporosis group,and between reduced bone mass group and osteoporosis group.Spearman correlation analysis showed that BMD was negatively correlated with age(r=-0.736,p<0.001).The difference in DAS28-ESR score of disease activity among the three groups was statistically significant.Tukey test results showed that the average DAS28-ESR score in the osteoporosis group was 1.61 higher than that in the normal bone mass group(95%CI:0.66～2.56),and the difference was statistically significant(p<0.001).There was no significant difference in DAS28-ESR scores among other groups(p>0.05).Spearman correlation analysis showed that BMD was negatively correlated with DAS28-ESR score of disease activity(r=-0.324,p=0.001).There were statistically significant differences in the cumulative amount of glucocorticoid(GC,based on equivalent prednison)and the duration of GC treatment among the three groups.Post-facto pairwise comparisons of the Bonferroni method for correcting significance levels found that the differences in GC accumulation and GC treatment duration between the normal bone mass group and the osteoporosis group were statistically significant,while the differences between the other groups were not statistically significant.Spearman correlation analysis showed that BMD was negatively correlated with GC accumulation and GC treatment time(r=-0.303,p=0.002;r=-0.281,p=0.004).Laboratory indicators:Erythrocyte Sedimentation Rate(ESR),C-reactive protein(CRP),alkaline phosphatase(ALP),peripheral blood leukocyte,monocyte,NK cell,albumin,Immune globulin(Ig)M,indirect bilirubin,urea,blood zinc,lactate dehydrogenase(LDH),α hydroxylbutyrate dehydrogenase(α-HBDH),total cholesterol(TCHO),free cholesterol(FCHO),high density lipoprotein cholesterol(HDL-C),low density lipoprotein cholesterol(LDL-C)differences were statistically significant among the three groups.3.There was no statistical significance in the use of disease-modifying anti-rheumatic drugs(DMARDs)among the three groups.However,t test results of independent samples indicated that mean BMD of lumbar 1-3 was higher in patients treated with DMARDs than in those not treated with DMARDs,with a difference of 17.44 mg/cm3(95%CI:1.90～32.97 mg/cm3).DAS28-ESR score in the group without DMARDs(6.14±1.58)was higher than that in the group with DMARDs treatment(5.33±1.86),the difference was 0.81(95%CI:0.11～1.51).The results of Mann-Whitney U test indicated that there was a statistically significant difference in peripheral blood monocyte between patients treated with or without DMARDs(U=867,P=0.004).The median number of peripheral blood monocyte in the group not treated with DMARDs was 0.56×10^9/L(n=40),and the median number of peripheral blood monocyte in the group treated DMARDs was 0.46×10^9/L(n=65).4.The difference of ethnic group(minority,Han)among the three groups was statistically significant(χ2=6.203,p=0.045).Pairwise comparison showed that the ethnic difference between the normal bone mass group and the osteoporosis group was statistically significant(p<0.05),while the ethnic difference between the other two groups was not statistically significant.Minority patients were more likely to develop osteoporosis than Han patients,with an odds ratio of 3.106(95%CI:1.143～8.440).T-test results of independent samples indicated that the average BMD of lumbar 1-3 vertebral bodies in Han patients was higher than that in minority patients,with a difference of 29.18(95%CI:10.36-48.01).In addition,there was no statistically significant difference in age,course of disease,GC accumulation,DAS28-ESR score,calcium supplementation,active vitamin D supplementation,DMARDs treatment,serum albumin,plasma cholesterol,myoenzyme,CRP,ESR and other indicators in Han/minority patients.5.Multiple stepwise regression analysis results showed that age(t=10.621,p<0.001),GC accumulation(t=3.001,p=0.003),the ethnic(t=3.865,p<0.001),CRP(t=2.791,p=0.006),peripheral blood monocyte(t=3.034,p=0.003),Creatine Kinase MB Isoenzyme(CKMB)/Creatine Kinase(CK)(t=2.986,p=0.004)are the main factors influencing lumbar BMD of the patients with RA.The regression model was statistically significant(F=39.218,p<0.001,and R2=0.698 after adjustment).The effects of the six independent variables included in the model on the mean BMD of the lumbar 1-3 vertebral body were statistically significant(p<0.05).Conclusions:1.QCT was used to measure lumbar BMD,and it was found that the proportion of OP in RA patients was high,which was consistent with the previous conclusions obtained by measuring bone mineral density using DXA;2.Variables were screened by multiple stepwise regression analysis,and then the regression equation for predicting the mean BMD of lumbar 1-3 vertebral body was obtained as follows:BMD=254.197-2.672×age(years)-0.332 X CKMB/CK(%)+21.93×[0/1(0=minority,1=Han)]-29.347×monocyte(×10^9/L)-0.154×CRP(mg/L)-1×GC accumulation(g).For medical institutions without BMD detection conditions,the value of BMD can be initially estimated to provide a basis for clinical prevention and treatment of patients with OP secondary to RA;3.In RA patients who had rational use of DMARDs,supplementation of active vitamin D,higher serum indirect bilirubin,higher serum IgG,IgM,Ro52-positive have higher lumbar BMD values;RA patients with lower albumin levels and longer duration had lower lumbar BMD values;4.The mean BMD of the lumbar 1-3 vertebral body of Han patients is higher than that of minority patients.The reason for this difference may be the result of the combined effect of multiple factors such as age,disease course,BMI,GC treatment,disease activity,calcium supplementation,active vitamin D supplementation,DMARDs treatment,serum albinin,plasma cholesterol,myozyme,inflammation,dietary habits,lifestyle,smoking,drinking,living environment and physical activity.Therefore,the sample size of minority patients should be further expanded for this study.