Application of the WHO fracture risk assessment tool (FRAX) to predict need for DEXA scanning and treatment in patients with inflammatory bowel disease at risk of osteoporosis

Abstract

Although patients with inflammatory bowel disease (IBD) are at increased risk of osteoporosis, low bone mineral density (BMD) alone confers only a modest increase in risk of fracture. The FRAX score, developed by the WHO, is a free web-based clinical scale assessing the 10-year fracture risk and need for lifestyle advice/reassurance, dual X-ray absorptiometry (DEXA) scanning or preventive treatment. To assess the accuracy of pre-BMD FRAX scores in identifying at risk IBD patients needing BMD measurement (intermediate risk) and/or therapy (high risk). We calculated FRAX scores retrospectively in 116 consecutive IBD out-patients (81 Crohn's disease, 35 ulcerative colitis), who were having DEXA scans in 2005-2009 because they were considered at risk of osteoporosis. On DEXA scans, 47% (38/81) and 12% (10/81) patients with Crohn's disease were osteopaenic and osteoporotic, respectively; equivalent figures for patients with UC were 34% (12/35) and 14% (5/35). The clinical FRAX score alone, when compared with the FRAX score including the BMD result, had a sensitivity of 100% (95% CI: 70-100%), specificity of 40% (95% CI: 31-50%), positive predictive value of 16% (95% CI: 9-27%) and negative predictive value of 100% (95% CI: 90-100%) in identifying those patients needing BMD measurement (intermediate risk) or preventive therapy (high risk). In patients with IBD perceived to be at risk of osteoporosis and/or osteopaenia, the clinical FRAX score alone can predict accurately the risk of osteoporotic fracture, and thereby reduce the need for DEXA scans and unnecessary anti-osteoporosis treatment.