Abstract
Introduction: Phase angle, derived from bioelectrical impedance analysis, is a consistent functional and prognostic indicator in health and disease states including cancer and heart failure. It reflects cellular mass and integrity, and its determinants include inflammation, nutritional status and muscularity. This study assessed the validity of phase angle as a health indicator in stable COPD via its relationship with established health outcomes.
Methods: In 502 stable COPD outpatients, phase angle as well as hand-grip and quadriceps strength, incremental shuttle walk (ISW) and 4-metre gait speed (4MGS) were measured. Patients were stratified according to normal and low phase angles; below 5th percentile sex, age and body mass index specific healthy reference values.
Results: There were significant positive correlations between phase angle and grip strength r=0.48, quadriceps strength r=0.66, ISW r=0.43 and 4MGS r=0.35 (p<0.001). Patients with a low phase angle had significantly reduced muscle strength and functional exercise capacity and reported more exacerbations and hospital days in the last year compared to those with a normal phase angle (p<0.01).
Conclusion: Phase angle is a valid indicator of health status in stable COPD and has potential as a simple prognostic tool in this population.
- © 2014 ERS