The Fracture Risk Assessment Tool (FRAX) can predict fracture probability effectively in patients with rheumatoid arthritis (RA) but not in those with systemic lupus erythematosus (SLE) or primary Sjögren syndrome, according to study results published in Lupus.

Researchers conducted this retrospective study of Taiwanese patients who had RA (n=451; 89.4% women; average age, 57.5 years), SLE (n=233; 94.4% women; average age, 47.4 years), or primary Sjögren syndrome (n=118; 87.3% women; average age, 59.7 years) to determine whether FRAX can be used to predict fracture risk in people with systemic autoimmune disease. Each participant was assessed for bone mineral density (BMD), antiosteoporotic medication use, and any osteoporotic fractures.

Compared with patients with SLE or primary Sjögren syndrome, patients with RA had a significantly lower average T-score and BMD at the bilateral femoral neck, but there was no significant difference at the lumbar spine.

A major osteoporotic fracture was recorded in 37.5% of participants, with incidence rates of 43%, 29.2%, and 33.1% in the RA, SLE, and primary Sjögren syndrome groups, respectively. For those with a previous osteoporotic fracture, the researchers noted that T-scores indicated normal or low bone mass and that BMD alone was likely inadequate to predict likelihood of a fracture.

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Omitting BMD, participants’ overall 10-year risk for a major fracture calculated by FRAX was 15.8%, which was below treatment threshold. With BMD included in the calculation, that rate increased to 20.3%, which warranted treatment initiation. When stratified by disease, FRAX predicted risk accurately in patients with RA, but underestimated risk in patients with SLE and primary Sjögren syndrome (with and without BMD measurements). However, for patients with primary Sjögren syndrome who had major osteoporotic fractures, FRAX risks imputed by RA were similar to major osteoporotic fracture risks in patients with RA.

Limitations to this study included the small sample of patients with hip fracture as well as that disease activity was not considered in the data, which may have led to underestimation of fracture risk.

“[O]ur study demonstrates that patients with autoimmune diseases are at high risk of developing osteoporotic fractures, even when their BMDs are still within the ‘low bone mass’ category,” said the researchers. “The current FRAX calculation is unable to accurately predict fracture probability among SLE and [primary Sjögren syndrome] patients, which thus precludes the use of timely and effective preventive therapy in these patients.”

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Reference

Lai EL, Huang WN, Chen HH, et al. Ten-year fracture risk by FRAX and osteoporotic fractures in patients with systemic autoimmune diseases [published online June 9, 2019]. Lupus. doi:10.1177/0961203319855122