Relationship between Bio-Impedance Phase Angle and Lung Function in Children and Adolescents with Cystic Fibrosis

Objectives: Pulmonary dysfunction is the main cause of mortality in cystic fibrosis and has a close relationship with malnutrition. Therefore, early detection of malnutrition is essential to starting nutritional interventions as soon as possible. Routinely BMI-Z-Score is used as a marker of malnutrition. To evaluate whether body composition may be a better predictor of malnutrition, the standardised phase angle (SPhA) is determined for comparison.

Methods: We divided 156 children and adolescents with cystic fibrosis according to the severity of pulmonary dysfunction into normal dysfunction (NF n=120; FEV₁% ≥ 75%) and severe dysfunction (SF n=36; FEV₁%<75%) groups, using FEV₁% measured by spirometry for classification. To assess nutritional status, we calculated the BMI-Z-Score and determined the SPhA with bio-impedance analysis.

Results: An intraclass-correlation showed no agreement between BMI-Z-Score and SPhA. Stepwise multiple regressions with FEV₁% as the dependent variable showed that BMI-Z-Score was the only significant predictor in NF and accounted for 16% of the observed variance. In SF, 34% of the variance was explained by SPhA.

Conclusion: SPhA may be a better prognostic indicator of severe pulmonary dysfunction in children and adolescents with cystic fibrosis than BMI-Z-Score. Therefore, the early recognition of malnutrition by SPhA may improve clinical outcomes through earlier initiation of nutritional interventions.