[Risk factors for bone mineral density changes in patients with rheumatoid arthritis and fracture risk assessment].

OBJECTIVE

To verify the fracture risk assessment tool (FRAX) to estimate the probability of osteoporotic fracture in patients with rheumatoid arthritis (RA) with or without bone mineral density (BMD), and identify associated risk factors of osteoporosis.

METHODS

In the study, 200 patients with rheumatoid arthritis aged more than 40 years in Peking University First Hospital from Dec. 2009 to Dec. 2012 were recruited. Clinical information was obtained from a questionnaire of their case history and medical records. FRAX tool was administered. Their lumber spine and left femoral BMD were determined by dual energy X ray absorptiometry. The gender, age, disease duration, menopause status, body mass index (BMI) and accumulative dose of glucocorticoid were obtained in retrospect. Correlation analysis was conducted between the BMD and clinical information.

RESULTS

The study population (female, 77.5%) had a mean age of 59.4 years, in which 10 (13%) patients showed a normal BMD, 67 (87%) were osteopenia or osteoporosis, while 32 patients (16%) had fragile fracture. Compared with the patients with normal BMD, the subjects with low BMD had significantly older age, longer period for corticoids usage, higher day dose and accumulated dose of corticoids.The 10-year fracture risk of sustaining major osteoporotic fractures and hip fracture was higher. No significant difference was observed between the 10-year fracture risks calculated with BMD and without BMD. The values of the different area under the receiver operating characteristic (ROC) curve (AUC) for major and hip fractures calculated in three ways: without BMD, with the femoral neck BMD, and with T-score. The best result was for FRAX tool for hip fracture with the T-score (AUC 0.899). A stepwise multivariate linear regression model was constructed to explore the relationship between the different clinical factors studied and a low BMD. Three statistically significant variables for lumber BMD were pain on visual assessment scale (VAS) (P=0.02), fracture history (P=0.003) and a higher steroid accumulated dose (P=0.008). Three statistically significant variables for left hip BMD were age (P<0.001), fracture history (P=0.05) and lower BMI (P=0.03).

CONCLUSION

Low BMD is a common complication in RA patients. Risk factors for major fracture and hip fracture are increased. There is a positive correlation between FRAX calculated with and without BMD or T score. FRAX with the femoral neck T score or BMD presents a discriminatory capacity better than FRAX without BMD, according to the AUC ROC.