Utility of phase angle in children with intestinal failure

Bioelectrical impedance analysis-derived phase angle has been gaining attention in clinical research as a potential biomarker of cell membrane integrity, which may reflect aspects of nutritional status, muscle quality, and overall cellular health. Although phase angle has been associated with various conditions, including malnutrition and reduced strength, it is not currently established as a definitive tool for assessing these outcomes. Rather, it is considered an indirect indicator, with lower values suggesting potential alterations in cell membrane function that may occur in the context of disease or malnutrition. The aims of this study were to 1) compare bioelectrical impedance analysis-derived phase angle in children with intestinal failure to that of healthy literature controls; 2) examine the relationship between phase angle and nutritional status variables in this cohort of children with intestinal failure.

Prospective descriptive cross-sectional study in a cohort of children 1-18 years with intestinal failure. Phase angle was calculated from reactance and resistance values derived from bioelectrical impedance analysis measurements as follows: [arctangent (Reactance/Resistance) x 180°/π]. Anthropometric measurements including weight, height, mid-upper arm circumference and triceps skinfold thickness, and mid-upper arm muscle circumference was calculated. Body composition was measured by dual energy X-ray absorptiometry as part of routine monitoring. Strength and physical activity were assessed by handgrip strength and accelerometry, respectively. Data on subject characteristics were collected. Two-sample t-test was used to compare phase angle of children with intestinal failure to healthy age and sex matched literature controls. Regression analysis was used to assess the relationship between phase angle and nutritional status variables.

Sixty-eight children with intestinal failure, mean age 8.9 ± 4.2 years, 25 dependent on parenteral nutrition were studied. Children with intestinal failure had lower phase angle compared to literature controls (5.0 vs 6.0, p < 0.001). Phase angle scores were found to be significantly associated with mid-upper arm circumference (r² = 0.27, p = 0.002), handgrip strength (r² = 0.29, p = 0.003), and mid-upper arm muscle circumference (r² = 0.29, p < 0.001). All relationships were positively mediated by age.

These findings suggest that phase angle may provide valuable insights into muscle mass and strength aspects of health beyond conventional assessments, but further study is required before incorporating it into clinical practice for assessing children with intestinal failure.