Biochemical and anthropometric correlates of bio-electrical impedance parameters in severely malnourished children: A cross-sectional study

Abstract

Introduction: Despite expanding use of bio-impedance (BI), little is known about its pathophysiologic significance and biological correlates OBJECTIVE: Determine correlations of BI parameters with anthropometry and biomarkers of electrolyte homeostasis, inflammation and liver function in children with severe acute malnutrition (SAM).

Methods: We studied Ethiopian children with SAM (mid-arm circumference <11·0 cm or weight-for-height <70% of the NCHS growth reference median and/or nutritional oedema) at hospitalization. Impedance (Z, Ohm), resistance (R, Ohm), reactance (Xc, Ohm) and phase angle (PA, degree) were measured at 50 kHz. R and Xc were height-indexed. Anthropometric Z-scores were calculated. Serum phosphate, Ca, Na, K, Mg, alkaline phosphatase, bilirubin, α1-acid glycoprotein, albumin and haemoglobin were measured. Healthy children were used for BI comparison. Correlates of BI were established using forward selection after comparing models using likelihood ratio test.

Results: The sample comprised 55 children with SAM (age 36 ± 24 months; 60% males; 72.7% oedematous) and 80 healthy control children (age 28 ± 15 months; 47.5% males). Oedematous children had the lowest BI parameters compared with reference and non-oedematous children. Similarly, they had lower serum albumin, K and alkaline phosphatase levels than non-oedematous children. Oedema was independent negative correlate of R, Xc and PA. Serum albumin level and weight-for-height Z-score were positive correlates of R, whereas serum calcium and Cl levels were positive correlates of Xc. MUAC correlated positively with PA.

Conclusion: Nutritional oedema explained the divergence of BI parameters from normality. Soft tissue mass, serum albumin, Ca and Cl accounted for variability of BI parameters in children with SAM.

Keywords: Bio-electrical impedance; Biochemical; Correlates; Malnutrition; Severe acute.