The value of whole-body dual-energy x-ray absorptiometry in assessing body composition in patients with inflammatory bowel disease: a prospective study

Objectives Low skeletal muscle index (SMI) is common in inflammatory bowel disease (IBD) but has an uncertain relationship with active intestinal inflammation. This study evaluated body composition by whole-body dual-energy X-ray absorptiometry (DXA) in patients with IBD and healthy controls to enable the value of formal body composition analysis to be judged. Methods Patients with IBD and sex/age-matched controls prospectively underwent full body composition assessment by DXA, assessment by BMI, eating questionnaires and handgrip strength. Disease activity was assessed by faecal calprotectin (active ≥150 µg/g). A cohort undergoing biologic induction therapy were assessed at baseline and after ≥13 weeks. Results Total fat mass was higher in 54 patients with IBD (56% Crohn's disease, 61% male) than in 30 controls (median 25.1 vs. 18.7 kg, P = 0.042). DXA offered little more than BMI. Low SMI was more common than in controls (15% vs. 0%, P = 0.027). A normal BMI was seen in many patients with low SMI and handgrip strength was a poor marker of change in SMI. Body composition was similar in 28 patients with active vs. 22 with inactive disease. However, SMI increased specifically by 9.7% (P = 0.004) and BMI by 6.4% (P = 0.012) in 9 responders to therapy. Conclusion DXA identifies many patients with reduced SMI who are not detected by standard methodologies. While disease activity is not associated with low SMI, resolution of inflammation leads to improved SMI. The potential for recognition of such patients to influence therapeutic decisions underlines the need for DXA assessment in clinical practice.