Osteoporosis screening and fracture risk assessment in patients with inflammatory bowel disease

Abstract

Introduction: Patients with inflammatory bowel disease (IBD) have an increased risk of osteoporosis. The Fracture Risk Assessment Tool (FRAX) evaluates the fracture risk of individuals in the general population. IBD-specific risk factors of osteoporosis remained unclear. In 2008, the Dutch IBD-guideline (IBDG) formulated a high-risk profile of osteoporosis based on IBD-specific risk factors. This study assessed the accuracy of the IBDG-based osteoporosis screening using the FRAX-tool as reference. Methods: Adult IBD patients attending the gastroenterology outpatient unit were screened for osteoporosis using the IBDG and FRAX-method. Patients were not previously diagnosed with osteoporosis. Patient characteristics and medication usage were collected by a questionnaire and the medical record. Fracture risk was calculated without bone mineral density using the online FRAX-tool. Quartiles were stratified based on the 10-year probability of a major osteoporotic (MO) fracture and hip fracture, with the highest quartiles of risk used as reference (SPSS 17.0). According to the IBDG, patients with ≥1 of the following characteristics are at risk of osteoporosis: low energy fracture, multiple fractures in the past, systemic glucocorticoids (>1 year, >7.5 mg daily for six months), IBD since child age, inflammation of small intestines, short bowel syndrome, colestyramine usage, lactose/ calcium deficient diet, postmenopausal women, and age >55 years in men. Results: 287 Patients were included with a mean age of 48.5 years (SD 14.7). Mean 10-years probability was 4.2% (1.5-20.0%) for MO fracture and 0.9% (0.1-10.0%) for hip fracture. The number of patients classified in the highest risk quartiles for MO and hip fractures, were respectively 70 (24%) and 66 (23%). 195 Patients were classified as high risk by the IBDG. Sixty-six percent of these patients had MO and hip fracture risks in the three lowest quartiles (respectively <4.8% and <0.8%) leading to positive predictive values of respectively 34% and 33%, and negative predictive values of 97% and 100%. Conclusion: Based on the IBDG, two-third of the patients is at risk of osteoporosis. Although most patients in the highest fracture risk quartiles are recognized by the IBDG, this guideline lacks accuracy caused by low positive predictive values. Furthermore, this study shows that high-risk IBDG patients have relatively low fracture risks according to the FRAX-method.