Abstract: TH-PO926

Validation of Body Composition by Dual-Energy X-Ray Absorptiometry and Bioelectrical Impedance Analysis in Renal Transplant Recipients

Session Information

Category: Transplantation

  • 1702 Transplantation: Clinical and Translational

Authors

  • Wilkinson, Thomas James, University of Leicester, Leicester, United Kingdom
  • Richler-Potts, Danielle, Leicester Kidney Exercise Team, Leicestershire, Leicester, United Kingdom
  • Neale, Jill, Leicester Kidney Exercise Team, Leicestershire, Leicester, United Kingdom
  • Smith, Alice C., John Walls Renal Unit, Leicester General Hospital, Leicester, United Kingdom
Background

Renal transplant recipients (RTR) experience adverse body composition (BC) changes including obesity and muscle wasting. Aberrant BC is associated with poor physical function and graft recovery, and increased mortality. Measuring BC is vital to understanding health status and comorbidity prognosis. Whilst dual-energy x-ray absorptiometry (DXA) is seen as the gold-standard, bioelectrical impedance analysis (BIA) may be an accessible and cheaper alternative. Formulas using anthropometric data that estimate BC may provide an alternative where DXA or BIA is not available. However, due to fluid and metabolic disturbances as a result of renal impairment, these methods need to be validated. We aimed to assess the validity of BIA and the Hume formula against DXA in RTR.

Methods

36 RTR (12 females; 52±12 years; eGFR 54±21ml/min/1.73m2) were measured using DXA and BIA. Estimated lean mass (LM), fat mass (FM), and FM% were compared using regression and Bland-Altman plots. Using only age, sex, height and weight, BC was estimated using the Hume (1966) formula.

Results

BIA showed ‘excellent’ agreement against DXA (LM r=.98, FM .95, FM% .92). Bland-Altman bias showed that BIA tended to marginally overestimate LM (+2.1kg 95% limits of agreement -3.9-8.1), and underestimate FM (-2.1kg -8.6-4.3) and FM% (-3.8% -11.7-4.0). The Hume formula performed exceedingly well against DXA. Regression revealed ‘good’ to ‘excellent’ agreement for LM (r=.94), FM (.92), and FM% (.79). Like BIA, the Hume formula overestimated LM (+3.5kg -4.7-11.6) and underestimate FM% (-3.8% -11.7-4.0). Remarkably, FM from the Hume was nearly identical to DXA.

Conclusion

Compared to DXA, BIA is a valid and accurate measure of BC. Interestingly, BC (in particular, FM) can be accurately estimated using just age, sex, height and weight. Due to its ease, the Hume formula may provide another method using routinely collected data. As unfavourable BC is associated with adverse outcomes in RTR, it should be routinely measured. In the absence of DXA, BIA or the Hume formula are valid alternatives to estimate BC. Research should investigate the sensitivity of these methods following interventions.

Funding

  • Private Foundation Support