(218) Body Composition Changes of Paediatric Patients aged 6-18 years on Kaftrio using Bioelectrical Impedance (BIA)

Background: Body Mass Index (BMI) is a useful tool for predicting clinical outcomes. Two component measurements (fat and lean tissue) cannot be accurately determined by BMI. In some disease states, alterations in body composition are one of the primary symptoms. There is increasing evidence both of the poor ability of BMI to predict body fat in individuals and the value of information about lean mass (Wells et al., 2012). In children with CF, fat free mass is thought to be associated with improved respiratory function and outcome (Kljin et al., 2003).

DEXA can be useful in measuring compartments but there is limited reference data. Skinfold thickness data from 1970’s is available but it is an invasive technique.

Wells et al. has produced UK reference data using gold-standard 4 compartment model (including DEXA, waist circumference, BIA, total body water) for ages 5-20 years (2012) and most recently 2-5 years (2020) which can be used to reference across a variety of techniques including BIA. BIA is a non-invasive technique which uses low charge electrical currents to measure resistance at different frequencies against different tissues. Metabolically active lean mass and water are good conductors of current and will show low resistance. Fat mass and fat free mass in kg is divided by height (squared) to give Fat Mass Index (FMI) and Fat Free Mass index (FFMI).

Methods: We obtained consent for, and carried out BIA pre and 3-4 months post Kaftrio in a cohort of 9 patients, alongside weight, height, BMI, diet history, and DEXA as appropriate using a BIA machine suitable for ages 6 years and over. We provided bespoke advice regarding exercise/degree of fat reduction following this test. Exercise advice was either to promote weight bearing exercise for bone health or to increase energy expenditure (in the case of adiposity). We ensured that that the child has voided their bladder and is lying flat and still while the procedure is carried out. To reduce intra-observer error, the same clinician was used on each repeat measurement.

FMI and FFMI were calculated and compared with Reference Data centile charts (Wells et al., 2012).

Results: Results are shown in Table 1.
BIA was able to identify normal weight obesity, and likely early changes in adiposity alongside normal BMI. Low FFMI was also identified which is linked to poorer outcomes in CF.

Conclusions: BIA can identify normal BMI obesity, identify risk of adiposity or becoming overweight quicker than BMI or weight trend on centile chart. It helps to tailor information to the child and family and is useful for those who have impaired glucose tolerance in terms of showing risks of metabolic syndrome. It can give incentive for exercise adjustment, is non-invasive and quick and can identify, earlier than weight or BMI, the need for dietary change (such as reducing nutritional supplements or reducing food fortification).

Inter and intra-observer error remains an issue, which can be mitigated but reducing the number of clinicians carrying out BIA and providing regular training.

A series of simple ‘swaps’ provided for snacks

Acknowledgements:

References: Klijn P, Van der Net J, Kimpen J, Helders P, Van der Ent C. Longitudinal determinants of peak aerobic performance in children with CF. 2003; 124:2215-2219.