Prediction of low bone mineral density in patients with inflammatory bowel diseases

Background Low bone mineral density (BMD) remains a frequent problem in patients with inflammatory bowel diseases (IBD). There is no general agreement regarding osteoporosis screening in IBD patients. Methods Cases of low BMD and disease characteristics were retrieved from 3172 patients of the Swiss IBD cohort study. Multivariate logistic regression analysis was conducted for predictive modeling. In a subgroup of 877 patients, 253 dual-energy X-ray absorptiometry (DXA) scans were available for validation. Results Low BMD was prevalent in 19% of patients. We identified seven predictive factors: type of IBD, age, recent steroid usage, low body mass index, perianal disease, recent high disease activity and malabsorption syndrome. Low BMD could be predicted with a sensitivity of 79% and a specificity of 64%, a positive predictive value (PPV) of 35% and a negative predictive value (NPV) of 93%. The area under the curve of the receiver operating characteristics was 0.78. In the validation cohort we calculated a PPV of 26% and an NPV of 88%. Conclusion We provide a comprehensive analysis of risk factors for low BMD and propose a predictive model with seven clinical variables. The high NPV of models such as ours might help in excluding low BMD to prevent futile investigations.