Comparing Body Composition Assessment Methods

Background: Improvement in clinical care has resulted in longer life expectancy of children with intestinal failure (IF). However, recent data indicate that their body composition (BC) is abnormal with a relatively high fat mass (FM) and low fat free mass (FFM). Abnormal BC is linked to poor prognosis and increased length of hospital stay; yet BC is not assessed in pediatric clinical practice. Instead, growth charts which lack sensitivity to detect changes in BC are used. Physical activity (PA) is the most important predictor of FFM and increased PA contributes to decreased FM. Decreased PA in childhood is associated with increased FM and decreased FFM which are linked to diabetes and cardiovascular disease in adulthood. Dual-energy X-ray Absorptiometry (DXA) is considered the reference method for measuring BC in the clinical setting but it is expensive and not suitable for routine use. Bioelectrical Impedance Analysis (BIA) on the other hand is relatively inexpensive and non-invasive but needs to be validated for use in patients with IF. Objectives: 1) validate BIA against DXA as a clinical tool for monitoring changes in BC in children with IF, 2) quantify PA levels using activity counts from accelerometers and 3) assess strength. Design: 1-18 years, with IF followed by the intestinal rehabilitation program at SickKids. All subjects receiving a DXA for routine clinical monitoring are eligible. BIA and muscle strength will be measured in clinic. Demographic data and IF related factors including height, weight, PN prescription, age, diagnosis, bowel length and length of time off PN for those who have achieved enteral autonomy will be obtained. DXA measurement will be done by Diagnostic Imaging at SickKids. Patients will be fitted with an accelerometer to be worn for 7 days. Statistics: Differences between sexes will be assessed by t test. Relationship between PA and BC, and BC and muscular strength will be assessed by linear regression analysis. Agreement between DXA