FRAX (Australia) scores in women with impaired fasting glucose and diabetes

BACKGROUND: Diabetes is associated with higher fracture risk despite higher bone mineral density (BMD), with FRAX® underestimating risk. This study aimed to investigate FRAX score with and without BMD for women with normoglycaemia, impaired fasting glucose (IFG) and diabetes. METHODS: Among 566 women, aged 40–90 years, enrolled in the Geelong Osteoporosis Study, IFG was defined as fasting plasma glucose (FPG) ≥5.5 mmol/L and diabetes as FPG ≥ 7.0 mmol/L, use of antihyperglycaemic medication and/or self-report. FRAX (Australia) 10-year probabilities of major osteoporotic (MOF) and hip fracture were calculated, with and without BMD, producing four FRAX scores per participant. Kruskal-Wallis test for non-parametric data was used to examine differences between the three glycaemia groups. Fractures over 10 years were ascertained using radiological reports. The number of fractures predicted by FRAX was compared with the number of fractures observed using Chi-square tests. RESULTS: For MOF FRAX calculated without BMD, women with diabetes (n = 67) tended to have a higher median score 7.1 (IQR 2.7–12.0) than normoglycaemia (n = 252) (4.3 (IQR 1.9–9.9) and IFG (n = 247) (5.1 (IQR 2.2–9.6)). For hip FRAX without BMD, diabetes tended to have a higher score (2.5 (IQR 06–4.3)) than normoglycaemia (1.2 (IQR 0.3–4.1)) and IFG (1.3 (IQR 0.3–4.1)). In the normoglycaemia and IFG groups, MOFs were underestimated; 15 predicted vs 28 observed, p = 0.038; and 16 predicted vs 31 observed, p = 0.021, respectively. Fractures were accurately estimated in all other groups. When including BMD, the association with diabetes was non-significant for both MOF FRAX (normoglycaemia 3.7 (IQR 1.9–8.0), IFG 4.3 (IQR 2.2–8.1) and diabetes 5.3 (IQR 2.7–9.4)) and hip FRAX scores (normoglycaemia 0.6 (IQR 0.2–2.5), IFG 0.8 (IQR 0.2–2.7) and diabetes 1.0 (IQR 0.3–3.0)). For normoglycaemia and IFG, MOFs were underestimated (normoglycaemia: 13 predicted vs 28 observed and IFG: 13 vs 31). For diabetes, both MOFs and hip fractures tended to be underestimated by FRAX with BMD (MOF: 4 predicted vs 11 observed, p = 0.055, hip: 1 predicted vs 6 observed, p = 0.052). Hip fractures were accurately estimated in the normoglycaemia and IFG groups. CONCLUSIONS: Compared with women who had normoglycaemia or IFG, women with diabetes tended to have a higher FRAX score for both MOF and hip fractures when BMD was not included. When BMD was included, there was no difference. Fractures in diabetes tended to be underestimated by FRAX with BMD. This suggests that FRAX calculations including BMD may not be accurate for estimating fractures in those with diabetes.