Mid-Upper Arm Circumference

Mid-upper arm circumference is the girth of the upper arm measured at its midpoint. It reflects muscle and fat stores and is a rapid indicator of acute undernutrition. It is independent of age over a wide range and is not affected by oedema in the arm as strongly as weight.

It is a field tool that requires only a tape. It is widely used for community screening and triage.

Usage. It is used to identify acute malnutrition in children, to screen pregnant women and adults in nutrition programmes, and as a risk indicator when weight is hard to measure.

Preparation and technique. The left arm hangs relaxed. The midpoint is found between the tip of the shoulder (acromion) and the point of the elbow (olecranon) with the elbow flexed to 90 degrees. The tape is placed around the midpoint without compressing the skin, and the value is read to the nearest millimetre.

Children aged 6 to 59 months. Over 125 mm is normal. 115 to 125 mm indicates moderate acute malnutrition. Under 115 mm indicates severe acute malnutrition.

Adults and pregnant women. Cut offs differ between services. Under about 23 cm is commonly used to identify undernutrition in adults, and under about 21 to 23 cm identifies pregnant women at risk.

Interpretation.

• A low value in a child identifies acute malnutrition and the need for nutritional treatment.
• A value under 115 mm carries a high risk of death and warrants immediate referral.
• Mid-upper arm circumference identifies different children than weight-for-height, so the two are complementary.

Causes of a low value. Inadequate intake, malabsorption, chronic infection, HIV, tuberculosis, malignancy, and chronic disease.

Critical values and findings needing immediate action. A value under 115 mm in a child, or bilateral pitting oedema, requires urgent assessment for severe acute malnutrition and complications.

Limitations and artefacts. Inter-observer variability exists. Measurement must be at the midpoint. It does not detect chronic malnutrition or stunting. Values change little with age in young children, but adolescent thresholds differ.

Follow up tests. Weight-for-height z-score, assessment for bilateral pitting oedema, appetite test, blood glucose, haemoglobin, and tests for HIV and tuberculosis where indicated.

Special groups. Pregnant women use local cut offs. Older adults are interpreted with caution, because arm fat and muscle shift with age.