Possibilities of using a FRAX® risk calculator for 10-year probability of fractures assessment in patients with rheumatoid arthritis
Rheumatoid arthritis (RA) and glucocorticoid use are the most common causes of secondary osteoporosis (OP). Early detection of individuals at high risk for osteoporotic fractures among RA patients allows timely prevention of OP and its complications. Objective: to evaluate the diagnostic possibilities of using a FRAX® calculator without introducing femoral neck bone mineral density (BMD) into the algorithm, as well as different therapeutic intervention thresholds to identify RA patients who need anti-osteoporotic therapy. Subjects and methods. The investigation enrolled 97 RA patients aged over 50 years. A questionnaire survey and axial skeletal densitometry were made; the 10-year fracture risk was calculated using the FRAX® calculator with and without femoral neck BMD. The diagnostic characteristics (sensitivity, specificity, ROC-curves) of different therapeutic intervention thresholds (Russian and European age-dependent intervention thresholds; 20% and 10%) for FRAX) were studied. Results and discussion. The capabilities of the Russian FRAX® model with and without femoral neck BMD to identify patients requiring treatment for OP were very good (AUC=0.878+0.036 and AUC=0.872+0.040, respectively). Lumbar spine dual-energy X-ray absorptiometry also identified very well RA patients who should undergo prophylaxis against OP and related fractures (AUC=0.837+0.063), while femoral neck and whole hip BMD values showed lower accuracy in detecting these patients (AUC=0.587+0.102 and AUC=0.625+0.092, respectively). The Russian age-dependent threshold showed 79.7% sensitivity and 63.7% specificity in evaluating the FRAX® algorithm without BMD; these figures for FRAX® with BMD were 82.2 and 65.2%, respectively. The use of FRAX® without and with BMD revealed no significant differences in the identification of persons in need of treatment (x<sup>2</sup>=0.22; p=0.64). The sensitivity and specificity of other therapeutic intervention thresholds in determining the fracture risk with and without BMD were as follows: 90.4-94.6 and 17.4-21.7% for the European threshold; 58.8 and 93.8% for 20%, and 96.5% and 0 for 10%, respectively. Conclusion. The FRAX<sup>®</sup> calculator can be used to assess a fracture risk without entering the femoral neck BMD data into the algorithm for RA patients aged 50 years and older. Fracture risk should be assessed using the Russian age-dependent threshold that adequately identifies those who need OP treatment among RA patients.