Clinical Characteristics Of Chinese Patients With Rheumatoid Arthritis And Fragility Fractures

Objective:This study aimed to identify potential clinical risk factors of osteoporosis and fragility fracture in Chinese patients with RA.We comprehensively investigated the association between bone quality assessment methods including DXA,HR-pQCT,BTM and FRAX,as well as the value of combined tools in fracture risk evaluation.Methods:In this case-control study,RA patients were recruited from the Chinese Registry of rhEumatoiD arthrITis(CREDIT).Patients were included in osteoporotic fracture(OPF)group and control group according to their previous history of fragility fractures.Demographic data,traditional OP risk factors,female specific factors as well as RA clinical characteristics were collected.Serum bone turnover markers(P1NP,β-CTX and ALP),25(OH)D,PTH,TNF-a and IL-6 were examined.Lateral thoracolumbar X-ray,DXA and HR-pQCT were also performed for each participant.Firstly,clinical characteristics were compared between OPF and control groups to identify potential risk factors.Then,multivariate linear regression analyses were used to identify factors related to low BMD and decreased TBS.The level of serum BTMs were compared,and the associations between BTM,TBS and BMD were also assessed.In order to investigate alterations of HR-pQCT parameters in RA patients,age-and sex-matched healthy controls were included for comparison.These parameters were them compared between OPF and control groups to evaluate the association between bone microstructure and fractures.Finally,bone quality assessment tools were comprehensively analyzed.By comparing the AUCs of different combinations of measurements,their ability to identify fragility fracture were compared.Results:A total of 81 RA patients were enrolled in this study(11 patients in the OPF group and 70 in the control group).Mean age and gender distribution were similar between two groups.Patients in OPF group had lower BMI,lower grip strength,longer duration of RA,higher disease activity,higher HAQ-DI,higher rate of GC treatment and later menarche age,which were potential risk factors of fragility fractures.Multivariate linear regression indicated that old age,low BMI,low grip strength and ever GC treatment were negatively related to BMD.Old age and GC therapy were also related to decreased TBS.BTMs including P1NP,β-CTX and ALP were not significantly different between OPF and control groups.However,their levels significantly related to BMD and TBS.Compared with healthy controls,HR-pQCT of RA patients showed alterations in various bone parameters.Patients with OPFs and controls also had significantly differences in bone geometry,volumetric bone density as well as microstructure.TBS showed independent ability in the evaluation of bone microstructure(such as inhomogeneity of networks),but it failed to improve the ability to identify OPFs as a complementary factor of BMD(AUC=0.876 vs.0.874).Combination of DXA parameters and cortical porosity(HR-pQCT microstructure parameter)demonstrated better ability to detect OPFs(AUC=0.922).FRAX tool adjusted by BMD and TBS showed better discrimination of fracture risk in the future.Conclusions:Risk of OP and OPF in patients with RA is related to both traditional OP factors and RA specific factors.Bone turnover markers may be related to the mechanism of bone loss and microstructure impairment in RA patients.HR-pQCT can effectively distinguish RA patients with or without OPFs.The complementary role of TBS in fracture risk assessment was not shown in this study.Cortical porosity measured by HR-pQCT has the potential to be introduced to the existing system.Integration of new parameters may help improve the accuracy of fracture risk assessment in RA patients.