Examining Mid-Upper Arm Circumference Malnutrition z-Score Thresholds.

Area of Science:

• Pediatric Nutrition
• Anthropometry
• Malnutrition Diagnosis

Background:

• Common anthropometric z-scores (BMIz, WLz, MUACz) for malnutrition diagnosis have identical thresholds but are not fully concordant.
• Existing thresholds may not accurately reflect a child's true nutritional status.

Purpose of the Study:

• To critically examine mid-upper arm circumference z-score (MUACz) thresholds for their ability to correctly classify nutrition status in children.
• To assess the concordance and accuracy of anthropometric z-scores in diagnosing malnutrition.

Main Methods:

• A 2-year prospective single-center study involving 10,401 children aged ≤18 years.
• Estimated sensitivity, specificity, and predictive performance of malnutrition classification thresholds against clinician-based assessments.
• Analyzed distributions of weight-for-length (WLz), body mass index (BMIz), and MUACz z-scores.

Main Results:

• Participant z-scores indicated they were smaller and shorter than the reference U.S. population.
• Broad and overlapping distributions of MUACz, BMIz, and WLz were observed between nutrition classification groups.
• Misclassification rates increased with malnutrition severity, from 8% (no malnutrition) to 71% (severe malnutrition).

Conclusions:

• The sensitivity of proposed MUACz thresholds decreases with increasing malnutrition severity, necessitating optimization.
• Current thresholds do not accurately classify all children, leading to significant misclassification, particularly in severe cases.
• Further refinement of thresholds is required to minimize misclassification and accurately identify children at risk.