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

Abstract

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). We studied Ethiopian children with SAM (mid-arm circumference <11·0cm 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 50kHz. 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. 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. 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.