Body composition assessment of children undergoing treatment for cancer

All children participating in the study will have their height and weight measured on arrival at the centre. The Paediatric Oncology Assessment Tool will be completed before any body composition measurements are taken. Mid arm circumferences will be taken using a tape measure and following standard guidelines. Skinfolds will be measured using calibrated calipers and following the strict standard site protocol. Measurements will be taken at the biceps, triceps, subscapular and suprailiac sites. Total body potassium (TBK) analysis will be performed using a shadow shield whole-body counter (Accuscan, Canberra Industries, MA, USA), which contains three sodium iodide crystal scintillation detectors arranged above a scanning bed. The crystals detect the 1.46MeV gamma rays being emitted by the potassium-40 (40K) found in the body. As a fixed proportion of the body’s potassium occurs as the natural isotope 40K, TBK can be determined. The measurement of TBK will require the subject to lie supine on a bed that is moved under the detectors. Two 1100sec scans will be performed for each subject with all personal metallic objects having been removed. Background and sensitivity checks will be completed daily and considered in each measurement, with TBK in grams being reported. Body cell mass (BCM) will then be calculated from TBK and adjusted for body size (BCM/HTp). BCM/HTp will be expressed as a Z score relative to laboratory reference data. ADP measurement will be performed using the Bod Pod (registered trademark) Body Composition System, adhering to the manufacturer’s instructions (Life Measurement Inc, Concord, CA, USA; software version 1.69). Prior to each measurement, the Bod Pod will be calibrated at zero litres and with a standard calibration cylinder of 50 litres. The child is required to wear a swimming costume and swimming cap (both may be provided by the laboratory, specially laundered, if the child does not have their own) during the test. Body volume measurements will be taken as the subject sits inside the chamber for a 50 second period. The measurement will be completed twice or until the body volume measurements are within 150ml or 0.2% of each other, whichever was the smallest (maximum of three attempts). The average of the two successful measurements will be taken. The thoracic gas volume is then measured using the Bod Pod while the child breaths into a disposable tube. The ADP measurement will take approximately 10 minutes. Percent fat measurement will be estimated from the body volume measurements, using child specific equations. All testing will take place during 1 visit and take approximately 1.5 hours.