Bone density threshold and other predictors of vertebral fracture in patients receiving oral glucocorticoid therapy.

OBJECTIVE: To evaluate predictors of vertebral fractures, including a threshold for bone mineral density (BMD), in patients receiving oral glucocorticoids (GCs). METHODS: Data were obtained from 2 randomized clinical trials (prevention and treatment trials of risedronate) using similar methods, but different inclusion criteria were applied with regard to prior exposure to GCs. Predictors of vertebral fracture in the placebo group were identified using Cox regression with forward selection. The BMD threshold analysis involved a comparison of the 1-year fracture risk in postmenopausal women receiving placebo in the GC trials with that in postmenopausal women not taking GCs in 3 other trials. RESULTS: The study population comprised 306 patients with baseline and 1-year followup data on vertebral fractures (111 receiving placebo and 195 receiving risedronate). In the placebo group, the statistically significant predictors of incident fracture were the baseline lumbar spine BMD (for each 1-point decrease in T score, relative risk [RR] 1.85, 95% confidence interval [95% CI] 1.06-3.21) and the daily GC dose (for each 10-mg dose increase, RR 1.62, 95% CI 1.11-2.36). In the BMD threshold analysis, compared with nonusers of GCs, patients receiving GCs were younger, had a higher BMD at baseline, and had fewer prevalent fractures; nevertheless, the risk of fracture was higher in the GC users compared with nonusers (adjusted RR 5.67, 95% CI 2.57-12.54). The increased risk of fracture was observed in GC users regardless of whether osteoporosis was present. CONCLUSION: The daily, but not cumulative, GC dose was found to be a strong predictor of vertebral fracture in patients receiving GCs. At similar levels of BMD, postmenopausal women taking GCs, as compared with nonusers of GCs, had considerably higher risks of fracture.