What is Severe Acute Malnutrition (SAM)?
Severe Acute Malnutrition (SAM) is the most severe form of malnutrition, primarily affecting children under five years of age in low and middle-income countries. It results from a recent and rapid weight loss or a failure to gain weight, often combined with medical complications due to a compromised immune system. Children with SAM face a significantly higher risk of morbidity and mortality compared to their well-nourished counterparts. Early identification and management are therefore crucial to save lives and mitigate long-term health consequences.
The WHO Criteria for Diagnosing SAM
According to the World Health Organization (WHO), children aged 6 to 59 months are diagnosed with SAM if they meet at least one of three independent criteria:
- Low Mid-Upper Arm Circumference (MUAC): A MUAC measurement of less than 115 mm (<115mm).
- Low Weight-for-Height Z-score (WHZ): A WHZ score of less than -3 standard deviations (<-3 SD) of the median WHO Child Growth Standards.
- Presence of Bilateral Pitting Edema: The presence of nutritional edema on both feet.
For effective screening in a community setting, particularly in emergencies, the use of MUAC has been widely adopted due to its simplicity, speed, and reliability.
How MUAC Screening Works
The MUAC measurement is taken at the midpoint of a child's upper arm using a simple, color-coded tape. The tape is designed for children aged 6 to 59 months and provides a quick visual interpretation of the child's nutritional status.
- Green: A measurement that falls within the green section of the tape (>=125mm) indicates that the child is not acutely malnourished.
- Yellow/Orange: A measurement in this range (115mm to <125mm) indicates Moderate Acute Malnutrition (MAM). These children are at risk and require supplementary feeding programs.
- Red: A measurement that falls within the red section (<115mm) indicates Severe Acute Malnutrition (SAM) and carries a highly elevated risk of death.
Comparison of Diagnostic Tools: MUAC vs. WHZ
While both MUAC and WHZ are independent WHO-endorsed indicators for SAM diagnosis, they often identify different sets of malnourished children. This is a critical consideration for public health and humanitarian aid programs.
| Feature | Mid-Upper Arm Circumference (MUAC) | Weight-for-Height Z-score (WHZ) |
|---|---|---|
| Measurement Tool | Simple, color-coded tape | Weight scale and height/length board |
| Feasibility | Easy to perform, even with minimal training | Requires more equipment and trained personnel |
| Best for | Quick, community-level screening, especially in emergencies | Comprehensive clinical assessment |
| Bias | Tends to identify younger children with SAM | Can miss some children identified by MUAC |
| Concordance | Poor concordance with WHZ; they identify different children at risk | Poor concordance with MUAC |
| Screening Cut-off | <115mm for SAM | <-3 SD for SAM |
The Importance of Concurrent Assessment
Given the low concordance between MUAC and WHZ, many programs advocate for the use of both criteria where feasible to ensure comprehensive case-finding. Children with a low MUAC tend to be younger, whereas those with a low WHZ may be older, reflecting different underlying nutritional issues. Relying on one criterion alone could lead to the non-identification of a significant proportion of children with SAM.
Management Pathways Based on SAM Criteria
Once a child is diagnosed with SAM based on MUAC (<115mm), WHZ (<-3 SD), or bilateral edema, the next step is determining the appropriate management pathway. This is primarily guided by the child's clinical condition, specifically the presence of complications.
Inpatient vs. Outpatient Care
- Inpatient Management: Required for children with complicated SAM. This includes those with bilateral edema extending beyond the feet, medical complications like shock or severe anaemia, or a failed appetite test. Treatment occurs in a therapeutic feeding center or hospital setting.
- Outpatient Management: Suitable for children with uncomplicated SAM. This involves children with good appetite and no medical complications. They can be managed at home through community-based programs (CMAM) using Ready-to-Use Therapeutic Foods (RUTFs).
Conclusion: A Vital Tool in Malnutrition Response
The criteria for SAM MUAC, particularly the <115mm cut-off for children 6-59 months, is a cornerstone of modern malnutrition screening, especially in resource-constrained settings. It is an efficient, practical, and highly predictive tool for identifying children at a high risk of death due to severe wasting. While MUAC serves as a vital first-line screen, effective programs recognize its limitations and utilize it alongside other anthropometric indicators and clinical assessments. This multi-pronged approach ensures that as many affected children as possible are identified and receive the timely, life-saving nutritional and medical support they desperately need.
For more information on the WHO's Child Growth Standards, visit the National Institutes of Health website.
