Defining Severe Acute Malnutrition (SAM)
Severe Acute Malnutrition (SAM) is a life-threatening condition defined by severe wasting or bilateral pitting oedema. Mid-upper arm circumference (MUAC) measurement is a crucial tool for identifying individuals with SAM, especially in community settings where it is easier to implement than other anthropometric measurements like weight-for-height Z-score (WHZ). The cut-off point used for defining SAM with MUAC varies depending on the age group, and these guidelines are essential for effective screening and treatment.
MUAC Cut-Offs for Different Age Groups
The specific MUAC cut-off points vary across different populations. The most common application is for children aged 6 to 59 months, but guidelines also exist for older children, adolescents, and pregnant or lactating women.
MUAC cut-offs for children (6–59 months)
For children aged 6 to 59 months, the internationally accepted MUAC cut-off for defining SAM is less than 115 mm (<11.5 cm). The World Health Organization (WHO) updated this standard in 2009, increasing the cut-off from 110 mm to 115 mm to improve the identification of children at a higher risk of death. MUAC tapes designed for this age group often feature color coding to simplify the process, with red indicating SAM (<11.5 cm), yellow for moderate acute malnutrition (MAM) (11.5 cm to <12.5 cm), and green for a normal nutritional status (>=12.5 cm).
MUAC cut-offs for adolescents and adults
Screening for SAM in adolescents and adults often relies on different MUAC thresholds. A MUAC of less than 185 mm (<18.5 cm) is often used as a general indicator of SAM in adults (>=18 years). For adolescents between 15 and 17 years, the cut-off is also typically less than 185 mm, while for those aged 10 to 14, the threshold is lower, at less than 160 mm. These figures can vary depending on regional guidelines and specific contexts, particularly during humanitarian crises, as different organizations may set different thresholds based on local data and resource availability.
MUAC cut-offs for pregnant and lactating women
The nutritional status of pregnant and lactating women is critical for the health of both the mother and child. For pregnant women, a MUAC cut-off of less than 190 mm (<19.0 cm) is frequently used to indicate severe malnutrition. Some guidelines, especially in humanitarian settings, recommend a slightly higher, more conservative cut-off of less than 230 mm (<23.0 cm) to identify a broader population at risk for low birth weight infants. MUAC is particularly useful in this group because, unlike BMI, it does not change significantly during a normal pregnancy.
The Role of MUAC and Other Indicators
MUAC is a powerful and simple screening tool, particularly for community-level outreach, but it is not the only diagnostic criterion for SAM. Other indicators should be considered for a complete diagnosis and treatment plan, especially in a clinical setting.
Comparison of MUAC and WHZ
| Feature | MUAC (Mid-Upper Arm Circumference) | WHZ (Weight-for-Height Z-score) |
|---|---|---|
| Application | Primary screening tool in community settings | Gold standard for diagnosis in clinical settings |
| Logistics | Quick, simple, and can be used by community health workers | Requires accurate weighing scales and measuring boards, often resource-intensive |
| Diagnostic Value | High predictability for mortality risk | Standardized, compares a child's weight to their height against a reference population |
| Population | Most effective for children 6–59 months; also used for adolescents and adults | Children under 5 years old |
| Agreement with WHZ | Overlap exists, but not all children identified by MUAC are identified by WHZ, and vice versa | Defines SAM as <-3SD based on WHO standards |
The importance of bilateral oedema
Bilateral pitting oedema, a swelling caused by fluid retention, is a clinical sign that is also a definitive criterion for diagnosing SAM, regardless of a child’s MUAC or WHZ score. Its presence indicates severe malnutrition and requires immediate treatment. The assessment involves pressing a thumb on both feet for a few seconds; if an indentation remains, oedema is confirmed.
Conclusion
The MUAC cut-off is a cornerstone of global efforts to combat severe acute malnutrition, offering a rapid and reliable screening method for identifying at-risk individuals. The universally recognized cut-off of <115 mm for children 6–59 months, along with specific thresholds for older age groups, provides a consistent basis for action. However, its use in conjunction with other clinical signs like bilateral oedema ensures a comprehensive and accurate diagnosis. By training community health workers and caregivers to utilize MUAC tapes effectively, organizations can facilitate earlier detection and intervention, ultimately saving lives and improving health outcomes in vulnerable populations.
For more detailed information on nutrition assessment and training materials, you can visit the Food and Nutrition Technical Assistance (FANTA) Project's website.
Key MUAC Cut-Offs and Indicators
- Children (6–59 months): The definitive MUAC cut-off for severe acute malnutrition is less than 115 mm (<11.5 cm).
- Children under 6 months: A MUAC of less than 110 mm is used to identify infants at risk of poor growth and development.
- Adolescents (10–14 years): The cut-off for SAM is less than 160 mm (<16.0 cm).
- Adolescents (15–17 years) and Adults: A MUAC of less than 185 mm (<18.5 cm) indicates SAM.
- Pregnant/Lactating Women: The MUAC cut-off for severe malnutrition is less than 190 mm (<19.0 cm), though other thresholds may apply.
- Bilateral Oedema: The presence of bilateral pitting oedema is an independent diagnostic criterion for SAM, regardless of MUAC measurement.
- Community Screening: MUAC is a practical and robust tool for screening malnutrition at the community level, especially when color-coded tapes are used.
- MUAC vs. WHZ: MUAC and Weight-for-Height Z-score (WHZ) are distinct diagnostic criteria that identify different, but overlapping, populations of malnourished children.
References
- The Aga Khan University. "Mid-upper arm circumference assessment and comparison with weight." https://scholars.aku.edu/files/70315492/Mid-upper%20arm%20circumference%20assessment%20and%20comparison%20with%20weight.pdf
- World Health Organization (WHO). "WHO Child Growth Standards and the Identification of Severe Acute Malnutrition in Infants and Children." https://www.ncbi.nlm.nih.gov/books/NBK200776/
- National Institutes of Health (NIH). "WHO guideline on the prevention and management of wasting and nutritional oedema (acute malnutrition)." https://www.ncbi.nlm.nih.gov/books/NBK601660/
- Food and Nutrition Technical Assistance III Project (FANTA). "How to Measure MUAC (linked to Module 2 of NACS User's Guide)." https://www.fantaproject.org/sites/default/files/download/MUAC-2.7-NACS-Users-Guide-Apr2016.pdf
