FRAX predicts fracture risk in kidney transplant recipients

The World Health Organization Fracture Risk Assessment Tool (FRAX) estimates the 10-year fracture probability. We assessed the prognostic value of FRAX in kidney transplant recipients, as its utility in recipients is unknown.

We considered 458 individuals (mean age 45 years, 64% men) who received a kidney transplant in the province of Manitoba, Canada at the time of their first bone mineral density (BMD) test posttransplant (mean 1.1 years posttransplant; transplant years 1996-2011). FRAX probabilities were calculated from baseline information (age, sex, clinical risk factors, with or without BMD). Recipients were followed a mean of 6.4 years (interquartile range 3.0-10.0 years) after cohort entry for an incident major osteoporotic fracture.

In follow-up, 21 (4.6%) recipients experienced a major osteoporotic fracture. The observed 10-year major osteoporotic fracture risk of 6.3% (95% CI, 3.4-9.2%) was concordant with FRAX predictions (5.0% with BMD, 5.6% without BMD). Major osteoporotic fracture scores showed significant fracture prediction (hazard ratio per standard deviation, FRAX without BMD 1.66, 95% CI, 1.10-2.50; FRAX with BMD 1.64, 95% CI, 1.07-2.51). Area under the curve (AUC) for incident major osteoporotic fracture discrimination (AUC: FRAX with BMD 0.62, 95% CI, 0.50-0.74) was similar to the general population.

FRAX scores categorized most kidney transplant recipients as a low-risk fracture group, and the low observed fracture rates were consistent with the 10-year fracture predictions. FRAX showed modest fracture prediction and discrimination similar to the general population. Independent validation is needed before clinicians can routinely use FRAX in kidney transplant recipients.