Clinical Study Of Serum Vitamin D Binding Protein In Patients With Rheumatoid Arthritis And Association With Secondary Osteoporosis

ObjectiveTo explore the changes of serum vitamin D binding protein(VDBP)levels in patients with rheumatoid arthritis(RA)and clinical significance of association between serum VDBP with secondary osteoporosis(OP)in RA.MethodsOne hundred and seventy-six patients were selected as the experimental group and 83 normal persons were randomly selected as the control group.It is necessary to record in detail the clinical indicators of RA patients,including gender,age,weight,height,number of joint pressure swelling and the specific time of morning stiffness.Laboratory indicators include C reactive protein(CRP),rheumatoid factor(RF),erythrocyte sedimentation rate(ESR),anti-cyclic citrullinated peptides(CCP),etc.The disease activity score in 28 joints(DAS28)and Sharp score were calculated by bimanual X-ray photography.Bone mineral density(BMD)of RA patients was measured by dual energy X-ray absorptiometry and graded according to the standard.Results(1)The serum VDBP concentration in RA patients was significantly higher than that in normal control group(413.83 ± 11.89 ng/ml vs 79.45 ± 11.66 ng/ml),t=20.082,P<0.01).The concentration of VDBP(384.4ng/ml)higher than P95 in normal group was selected as the positive value of VDBP,whereas the concentration lower than 384.4ng/ml in negative group.The positive rate of VDBP in RA patients was 67.05%(118/176),which was significantly higher than that in normal control group(4/83)(?2=87.651,P<0.01).(2)The ROC curve was made with the concentration of serum VDBP as the test variable.The results showed that the area under the curve of VDBP-RA(AUC)was 0.943,and the cut-off point of serum VDBP was 193.74 ng/ml(P < 0.01).Serum VDBP concentration was 193.74 ng/ml as the diagnostic value of RA.In RA group,serum VDBP concentration was higher than 193.74 ng/ml,accounting for 89.2%(157/176).In normal control group,serum VDBP concentration was 9.6%(8/83)higher than the cutoff point(?2=160.37,P<0.01).(3)Serum VDBP levels(>384.4ng/ml)were defined as VDBP positive group and < 384.4ng/ml as VDBP negative group.The incidence of OP in female RA patients with VDBP positive was significantly higher than that in negative group [41.9%(54/129),31.8%(14/44),?2= 4.325,P<0.05].According to the DAS28 score,RA patients were divided into two groups(DAS28<5.1 as non-severe activity,DAS28>5.1 as severe activity).The results showed that the VDBP level in the severe activity group of RA patients was higher than that in the non-severe activity group(P<0.05),and the DAS28 level in the VDBP positive group was significantly higher than that in the negative group(P<0.05).But the positive rate of VDBP in 25(OH)D deficiency group was higher than that in 25(OH)D deficiency group,but no significant difference [62.5%(5/8),75.6%(65/86),?2 = 0.659,P>0.05].(4)DAS28 was positively and linearly correlated with serum VDBP level in RA patients(r=0.252,P<0.05).Anti-CCP antibody concentration was negatively correlated with serum VDBP level(r=-0.150,P<0.05).(5)Multivariate logistic regression analysis showed that age,sex(1 for male,2 for female),body mass index,DAS28,VDBP concentration,vitamin D level,Glucocorticoid(Gc)(0 for Gc use,1 for non-Gc use)and Sharp score were selected as independent variables in this study,and the occurrence of OP(0 for non-OP,1 for OP)in strain selection was evaluated by logistic regression.This study found that women(P<0.05),age(P<0.01)and Sharp score(P< 0.05)were all risk factors for OP in RA patients.ConclusionThe serum level of VDBP increased significantly in RA patients.The disease activity of RA was related to the serum level of VDBP.The occurrence of OP in RA is closely related to the concentration of VDBP.