Association between anthropometric criteria and body composition among children aged 6-59 months with uncomplicated severe acute malnutrition: A prospective cohort study from South Sudan.

Children admitted by MUAC-only criteria were younger and more stunted at admission compared to WHZ-only admitted children.

• Study conducted in Aweil Centre, South Sudan with children aged 6-59 months with uncomplicated SAM
• Admission sample size was n=194, with n=127 reaching discharge assessment
• MUAC and Combined groups were younger and more stunted than the WHZ group at admission
• Between-group differences were analyzed using linear mixed effects models adjusted for age and sex

The Combined (MUAC and WHZ) group showed the most severe deficits across anthropometry, fat mass index, and phase angle at admission.

• Body composition was assessed via bioelectrical impedance analysis and triceps skinfold thickness
• Measures included fat mass (FM), fat-free mass (FFM), fat mass index (FMI), fat-free mass index (FFMI), total body water percentage (TBW), and phase angle (PhA)
• The Combined group had the most severe deficits across all measured anthropometric and body composition indicators at admission
• Phase angle, a bioelectrical impedance indicator of cellular health, was most depressed in the Combined group

The WHZ-only group exhibited the fastest recovery during outpatient therapeutic program treatment, with weight gain composed predominantly of fat-free mass.

• Fat-free mass accretion accounted for 82% of weight gain in the WHZ group during treatment
• The WHZ group showed the largest increases in fat-free mass index (FFMI) during treatment
• Recovery trajectory was assessed between admission and discharge using linear mixed effects models
• The WHZ group's recovery pattern was characterized as predominantly lean tissue accrual

The MUAC-only group accumulated predominantly fat mass during treatment with minimal fat-free mass gain and a decline in phase angle.

• Fat mass accounted for 78% of weight gain in the MUAC group during treatment
• Phase angle declined in the MUAC group during treatment, suggesting worsening cellular health or fluid distribution despite anthropometric recovery
• Minimal fat-free mass gain was observed in the MUAC group
• This pattern contrasted sharply with the 82% fat-free mass accrual seen in the WHZ group

The Combined group showed mixed fat mass and fat-free mass recovery patterns during outpatient treatment.

• The Combined group's recovery trajectory was intermediate between the MUAC-only and WHZ-only groups
• Both fat mass and fat-free mass were accrued in the Combined group, unlike the predominantly FM or FFM patterns seen in other groups
• Despite starting with the most severe deficits, the Combined group did not show the fastest or most complete recovery
• All groups reached standard anthropometric discharge thresholds despite divergent body composition trajectories

Standard anthropometric discharge thresholds were met by all groups despite distinct underlying body composition recovery patterns.

• Children in all three admission groups reached standard anthropometric discharge criteria
• Body composition and impedance indicators revealed heterogeneity in tissue gain patterns not captured by anthropometry alone
• Phase angle and FM/FFM ratios at discharge differed across groups despite similar anthropometric outcomes
• The authors note these findings suggest 'anthropometric recovery alone may not uniformly capture the full recovery pattern across SAM admission groups'

The three SAM admission criteria groups showed distinct vulnerability profiles, particularly in the MUAC and Combined groups.

• The study was designed as a prospective cohort with three groups: MUAC only, WHZ only, and Combined MUAC+WHZ
• Diagnosis criteria used were bilateral edema, MUAC, and/or weight-for-height z-score (WHZ)
• Body composition and impedance indicators suggested differential post-discharge vulnerability across groups
• The authors characterize findings as 'exploratory' and call for longitudinal studies evaluating whether body-composition differences at discharge predict subsequent clinical outcomes and post-discharge vulnerability