Bone Abstracts

Insulin-like growth factor 1 (IGF-1) is known to be a predictor of future osteoporotic fractures. Insulin-like growth factor binding protein 1 (IGFBP1) regulates the bioavailability of IGF-1 and thus in reason IGFBP1 also could be a fracture predictor. To our knowledge there are no previous studies published on the relation between the serum concentration of IGFBP1 and fractures.

This is a population-based prospective cohort study on 351 Swedish women aged 69–79 years at inclusion. These women were tested for serum IGFBP-1 at inclusion between 1999 and 2001. Follow up was performed 10 years later through Swedish medical records. The main outcome was a hip fracture.

The aims of this study were to evaluate whether IGFBP1 could predict hip fractures and further to compare predictive ability of IGFBP1 with the standard method FRAX. The data was analyzed with Cox regression. No participant was lost to follow up. The relation between IGFBP1 and the risk of a hip fracture was found to be positively linear. The age-adjusted risk of a hip fracture increased significantly by 2% for every unit increase in IGFBP1 (Hazard ratio (HR) 1.020, 95% CI 1.004–1.036). Surprisingly, this HR was not significantly altered by further adjusting for either BMI, the serum concentration of IGF-1 or for BMD of the femoral neck. The age-adjusted IGFBP1 had a Harrell’s c of 0.63 compared to 0.59 for FRAX which indicates that IGFBP1 has a predictive ability similar to that of FRAX. Harrell’s c is the equivalent to the area under curve (AUC) used in logistic regression, but designed for Cox regression models. For a model combining IBFBP1 with FRAX, Harrell’s c was 0.64.

In conclusion, IGFBP1 could predict hip fractures as good as FRAX and unexpectedly, the relation was not explained by differences in BMI, IGF-1 or BMD of the femoral neck.