Background: Risk for low trauma fracture is increased by >30% after ischemic stroke. Additionally, in the IRIS trial pioglitazone therapy prevented ischemic stroke but increased fracture risk. We derived a risk score to predict risk of fracture one year after ischemic stroke.
Methods: The Fracture Risk after Ischemic Stroke (FRAC-Stroke) Score was derived in 20,435 ischemic stroke patients from the Ontario Stroke Registry discharged from 2003-2012, using Fine-Gray competing risk regression. Candidate variables were medical conditions included in the validated World Health Organization FRAX risk score complemented by variables related to stroke severity. Registry patients were linked to population-based Ontario health administrative data to identify low trauma fractures (defined as any fracture of the femur, forearm, humerus, pelvis or vertebrae, excluding fractures resulting from trauma, motor vehicle accidents, falls from a height or in people with active cancer). The score was externally validated in 13,698 other ischemic stroke patients in the population-based Ontario stroke audit (2002-2012).
Results: Mean age was 72; 42% were women. Low trauma fracture occurred within 1 year of discharge in 741/20435 (3.6%); cumulative incidence increased linearly throughout follow-up. Age, discharge modified Rankin score (mRS), and history of arthritis, osteoporosis, falls and previous fracture contributed significantly to the model. Model discrimination was good (c statistic 0.72). Including discharge mRS significantly improved discrimination (relative integrated discrimination index 8.7%). Fracture risk was highest in patients with mRS 3 and 4 but lowest in bedbound patients (mRS 5). From the lowest to the highest FRAC-Stroke quintile the cumulative incidence of 1-year low trauma fracture increased from 1% to 9%. Predicted and observed rates of fracture were similar in the external validation cohort.
Conclusion: The FRAC-Stroke score allows the clinician to identify ischemic stroke patients at higher risk of low trauma fracture within one year. This information might be used to target patients for early bone densitometry screening to diagnose and manage osteoporosis, and to estimate baseline risk prior to starting pioglitazone therapy.