Fragility fractures in lupus patients: Associated factors and comparison of four fracture risk assessment tools

Abstract

Objective

Osteoporosis (OP) and fragility fractures (FF) are common comorbidities in patients with systemic lupus erythematosus (SLE). This study aimed to (1) assess the prevalence of these conditions in a cohort of SLE patients (2) evaluate the risk factors associated with FF, and (3) compare the accuracy of four different FF risk assessment algorithms to determine which performs better in this specific rheumatologic population.

Materials and Methods

We conducted a cross-sectional study with SLE women who underwent bone mineral density assessment by dual-energy X-ray absorptiometry (DEXA) within 3 months of their last visit. Conventional radiology methods were used to evaluate the presence of FF. The 10-year risk of osteoporotic fractures was estimated using four tools: DeFRA, FRAX (adjusted for GC dosage), GARVAN, and QFracture. The comparison of these computational tools was analyzed by the area under the receiver operating characteristic (ROC) curves.

Results

We analyzed 86 SLE patients with a median age of 56 years (IQR 12.1) and a median age at diagnosis of 34 years (IQR 17.2). The median T-score values at the femoral neck and lumbar spine were −1.6 (IQR 0.9) and −1.7 (IQR 1.1), respectively. Of the patients, 33 (38.4%) had OP, with 13 patients (15.1%) experiencing FF. Univariate analysis showed that the presence of FF was associated with thrombocytopenia (p = .01), hemolytic anemia (p = .0001), and the intake of cyclosporine A (p = .002), cyclophosphamide (p = .006), and rituximab (p = .001). The median 10-year risk of major FF for the four calculation tools were as follows: DeFRA 9.85 (IQR 8.6); FRAX GC 8.8 (IQR11.7); GARVAN 12 (IQR 8.2); QFracture 4.1 (IQR 5.8). We observed a significant correlation among all instruments evaluated (p < .0001); in particular, the best correlation was recorded between the FRAX GC and the DeFRA (r = 0.85). DeFRA was the best tool for this population with an AUC of 0.94 (p < .0001, CI 0.88–1).

Conclusions

OP is a common comorbidity in SLE patients, even in younger patients. FF appears to be more frequent in patients with hematologic involvement. The comparison of the four algorithms shows that DeFRA is the most accurate tool and should be applied to SLE patients.