Fracture risk tools performance and potential use in systemic lupus erythematosus

Area of Science:

• Rheumatology
• Osteoporosis Research
• Medical Imaging

Background:

• Skeletal fragility is a significant comorbidity in patients with systemic lupus erythematosus (SLE).
• The accuracy of existing fracture risk assessment tools, such as FRAX, in SLE populations is not well-established.
• There is a need to evaluate alternative or refined tools for accurate fracture risk prediction in SLE.

Purpose of the Study:

• To compare the discriminative ability of the Fracture Risk Assessment Tool (FRAX) and the Italian FRAX-derived tool (DeFRA) for predicting fractures in patients with SLE.
• To assess the performance of FRAX and DeFRA at specific operational thresholds for identifying patients at high risk of fracture.
• To evaluate the clinical utility of DeFRA in guiding targeted vertebral fracture assessment (VFA) in SLE.

Main Methods:

• Secondary analysis of the FRAIL cohort (NCT05590390) including 106 patients with SLE.
• Dual-energy X-ray absorptiometry with VFA and radiography were used to confirm vertebral fractures.
• 10-year major osteoporotic fracture probability was calculated using FRAX and DeFRA, with discrimination assessed via receiver operating characteristic curves and DeLong's test.

Main Results:

• DeFRA demonstrated a higher area under the curve (AUC) than FRAX for detecting newly identified vertebral fractures (0.834 vs. 0.681, p=0.022) and any vertebral fracture (0.902 vs. 0.770, p=0.013).
• At the threshold of DeFRA ≥20%, 9 out of 15 new fractures were identified (Number Needed to Scan [NNS]=1.78), outperforming FRAX ≥20% (7 fractures).
• Lowering the DeFRA threshold to ≥15% increased sensitivity to 10/15 fractures (NNS=2.0) without compromising specificity, confirmed by bootstrap validation.

Conclusions:

• The DeFRA tool significantly outperforms the standard FRAX tool in detecting vertebral fractures in patients with SLE.
• DeFRA provides a clinically efficient threshold for targeted VFA, potentially improving diagnostic strategies.
• These findings suggest DeFRA can aid in optimizing imaging strategies and glucocorticoid management for fracture prevention in SLE patients.