Comparison of fracture risk prediction among individuals with reduced and normal kidney function

Abstract

Background and objectives: The Fracture Risk Assessment Tool (FRAX) is widely used to predict the 10-year probability of fracture; however, the clinical utility of FRAX in CKD is unknown. This study assessed the predictive ability of FRAX in individuals with reduced kidney function compared with individuals with normal kidney function.

Design, setting, participants, & measurements: The discrimination and calibration (defined as the agreement between observed and predicted values) of FRAX were examined using data from the Canadian Multicentre Osteoporosis Study (CaMos). This study included individuals aged ≥40 years with an eGFR value at year 10 of CaMos (defined as baseline). The cohort was stratified by kidney function at baseline (eGFR<60 ml/min per 1.73 m(2) [72.2% stage 3a, 23.8% stage 3b, and 4.0% stage 4/5] versus ≥60 ml/min per 1.73 m(2)) and followed individuals for a mean of 4.8 years for an incident major osteoporotic fracture (clinical spine, hip, forearm/wrist, or humerus).

Results: There were 320 individuals with an eGFR<60 ml/min per 1.73 m(2) and 1787 with an eGFR≥60 ml/min per 1.73 m(2). The mean age was 67±10 years and 71% were women. The 5-year observed major osteoporotic fracture risk was 5.3% (95% confidence interval [95% CI], 3.3% to 8.6%) in individuals with an eGFR<60 ml/min per 1.73 m(2), which was comparable to the FRAX-predicted fracture risk (6.4% with bone mineral density; 8.2% without bone mineral density). A statistically significant difference was not observed in the area under the curve values for FRAX in individuals with an eGFR<60 ml/min per 1.73 m(2) versus ≥60 ml/min per 1.73 m(2) (0.69 [95% CI, 0.54 to 0.83] versus 0.76 [95% CI, 0.70 to 0.82]; P=0.38).

Conclusions: This study showed that FRAX was able to predict major osteoporotic fractures in individuals with reduced kidney function; further study is needed before FRAX should be routinely used in individuals with reduced kidney function.

Keywords: CKD; Fracture Risk Assessment Tool; clinical epidemiology; epidemiology; fracture; outcomes.

Figure 1.

Study cohort. ^†Individuals who died or were not reachable at year 11 were excluded because we would not able to obtain fracture data from these individuals. CaMos, Canadian Multicentre Osteoporosis Study.

Figure 2.

Mean predicted 5-year fracture risk from the Canadian FRAX tool (with and without BMD) and observed 5-year major osteoporotic fracture risk (Kaplan–Meier) according to eGFR. Error bars are 95% confidence intervals. BMD, bone mineral density; FRAX, Fracture Risk Assessment Tool.