Predicting Non-traumatic Incident Fractures on Rheumatic Disease Patients on Long-term Glucocorticoids

Abstract

Background: To identify contributors to non-traumatic incident fractures on rheumatic disease patients who are on long term glucocorticoids (LTGC) Methods: Two hundred and twenty patients on LTGC (110 with vertebral fracture and 110 without vertebral fracture) who participated in a cross-sectional study in 2014-2015 were invited to have repeated assessments on 1) aBMD using dual-energy X-ray absorptiometry (DXA), 2) volumetric BMD (vBMD), microstructure and bone strength assessment of the wrist and tibia using high-resolution peripheral quantitative computed tomography (HR-pQCT) and 3) spine radiographs in the 5th year. Clinical covariates were recorded on questionnaires, and Fracture Risk Assessment Tool (FRAX) score was calculated accordingly. Non-traumatic incident fracture over the 5-year were documented. Receiver operating characteristic curve (ROC) analysis was performed to compare the strength of fracture prediction tools. Results: Out of the 140 patients who completed the 5th year assessments, 47 (33.6%) developed incident fractures. History of previous fracture, aBMD at hip and lumbar spine, T-score, trabecular vBMD, trabecular bone volume fraction and estimated bone strength at the tibia at baseline remained significantly different after adjusting for age between the group with and without incident fractures. The area under curve (AUC) of a prediction model comprised of age, history of previous fracture and average trabecular vBMD at tibia was comparable with that of the FRAX score (0.710 vs 0.679-0.702), and slightly outperformed than the AUC of DXA aBMD at hip and lumbar spine (0.628-0.668) under ROC analysis. Conclusion: Age, history of previous fracture and average trabecular vBMD at tibia could be the main contributors in building a prediction model for non-traumatic incident fracture in rheumatic disease patients on LTGC.