Evaluating Mid-Upper Arm Circumference Z-Score as a Determinant of Nutrition Status

BACKGROUND Mid-upper arm circumference (MUAC) z-score, has recently been listed as an independent indicator for pediatric malnutrition. This investigation examined the relationship between MUAC z-score and the z-scores for conventional indicators (ie, weight-for-length and body mass index) to expand the available evidence for nutrition classification z-score threshold ranges in U.S. practice settings. METHODS This was a single-center study of children through 18 years of age seen between October 2015 and September 2016. Height and weight were obtained on intake. MUAC was measured at midpoint of the humerus, between the acromion and olecranon. Age-specific and gender-specific z-score values were calculated using published λ, μ, and σ values derived from Centers for Disease Control and Prevention reference data. Nutrition status was determined from biochemical data; prior history; anthropometrics; weight gain velocity; weight loss, if present; and nutrient intake. RESULTS 5,004 children (7.5 ± 5.7 years, 53% boys) were evaluated. As expected, MUAC z-scores were significantly correlated with body mass index (r = 0.789, P < .01) and weight-for-length (r = 0.638, P < .01) z-scores. There was a large degree of overlap in z-scores for all indicators between nutrition status groups; however, MUAC z-scores spanned a narrower range of values such that mean MUAC z-scores are lower in children classified as overweight/obese and higher in children who were severely malnourished than the corresponding body mass index or weight-for-length z-scores. CONCLUSION These data are the first to suggest that the z-score ranges used to define various stages of malnutrition may not be the same for all indicators.