Traditionally, weight, length/height, weight-for-length/BMI were used to identify pediatric malnutrition. In hospitalized children with special health care needs, obtaining a weight and length/height at admission can often be challenging, let alone getting an accurate measurement.

Acute illness can affect weight via fluid shifts (think edema, ascites or even steroid use) making their weight unreliable. The most critically ill children are often too unstable to weigh. Stunting can falsely under-diagnose malnutrition by affecting weight-for-length/height.

To address this problem, the American Society for Parenteral and Enteral Nutrition (ASPEN) and the World Health Organization (WHO) recommend measuring mid-upper arm circumference (MUAC), especially for those children between 6 and 60 months.


What is MUAC?

MUAC is assessed at the midpoint between the acromion process and olecranon process, and then compared to other children of the same age and sex.

This simple, quick and reliable measurement can be a better indicator than weight-for-length/BMI in those children who are critically ill.


When it comes to MUAC, ASPEN recommends the following:

✅ A trained professional (usually a dietitian) using standardized techniques

✅ Measure on admission and then serially (most of us do weekly in the inpatient setting)

✅ Record and plot on reference/standard age-appropriate curves to obtain the z-score, referenced below

✅ Classify the severity of existing/current nutrition state based on cutoffs


How to interpret the results?

<11.5 cm severely malnourished

between 11.5 and 12.4 cm moderately malnourished

between 12.5 and 13.4 cm at risk of malnutrition


Pearls:

Weight-for-length/BMI and MUAC should be used together to identify a child with undernutrition using the most severe indicator

Serial MUAC measurements can be used to monitor changes in body composition by using the child as his or her own control


Limitations:

Accuracy may be questionable in children with severe muscle wasting

Unreliable in children <6 months of age


What about older kids:

There are no WHO standards for older children and adolescents. There are percentile standards by Frisancho for ages 1-19 years (published in 1981). MUAC can still be used as a serial marker of changes in muscle and fat mass.


Helpful Resources:

WHO MUAC reference charts: https://www.who.int/childgrowth/standards/ac_for_age/en/

Check out our blog on Pediatric Malnutrition – Dietitians Make a Difference for more tools


Bottom line:

MUAC should be part of routine measurements, especially in children between 6-60 months and can be used as an independent predictor of malnutrition.


We’d love to hear from you.

Do you routinely measure MUAC in your practice?

Are you using it to identify malnutrition or even tracking it over time to follow changes in fat and muscle mass?


Stay safe!

Charlene and Julie

P.S. For more in-depth information on pediatric malnutrition, check out our signature course Infant Nutrition Essentials.

P.P.S Join our growing Facebook group: Pediatric Dietitians: Newbies to Masters