Accurate and timely diagnosis of severe acute malnutrition (SAM) is essential for effective treatment and intervention. The World Health Organization (WHO) has established clear guidelines for diagnosing SAM in children aged 6–59 months, based on a combination of anthropometric and clinical indicators. A child meeting any one of these three independent criteria is considered to have SAM.
The Three Key Indicators for Calculating SAM
The calculation and diagnosis of severe acute malnutrition rely on three primary, independent indicators. These can be measured by trained healthcare workers and, in some cases, community health workers for effective screening.
1. Mid-Upper Arm Circumference (MUAC)
MUAC is a simple, quick, and effective measurement used for field-based screening and is a strong predictor of mortality risk. For children aged 6-59 months, a MUAC measurement less than 115 mm (typically in the red zone of a color-coded tape) indicates SAM. Measurements between 115 mm and 125 mm (yellow zone) indicate Moderate Acute Malnutrition (MAM), and greater than 125 mm (green zone) is considered normal. You can find detailed instructions on how to measure MUAC in the referenced documents.
2. Weight-for-Height Z-Score (WHZ)
The WHZ is a standardized measure comparing a child's weight to a reference population of well-nourished children of the same height and sex. For children aged 6-59 months, a WHZ score of less than -3 standard deviations (SD) below the median indicates SAM. A score between -2 and < -3 SD indicates MAM, and a score greater than -2 SD is considered normal. Calculating WHZ requires measuring weight and height accurately and using WHO Child Growth Standards, often with the help of specialized software. More detailed instructions can be found in the provided sources.
3. Bilateral Pitting Oedema
Bilateral pitting oedema is a clinical sign of SAM and is considered a sufficient diagnosis on its own. To assess for oedema, apply firm pressure with your thumbs to the tops of both feet for three seconds. If a dent remains after removing your thumbs and it is present on both feet, the child has bilateral pitting oedema, a sign of SAM. More information on how to assess for oedema is available in the referenced document.
Comparison of SAM Diagnostic Methods
| Feature | Mid-Upper Arm Circumference (MUAC) | Weight-for-Height Z-Score (WHZ) | Bilateral Pitting Oedema |
|---|---|---|---|
| Ease of Use | Very easy and fast | Complex; requires special equipment and software for calculation | Simple to assess clinically |
| Equipment Needed | Simple, color-coded MUAC tape | Accurate weighing scale, measuring board, calculator or software | None, just a trained eye and hands |
| Use Case | Community screening and field assessments for rapid triage | Clinical settings and nutritional surveillance for higher accuracy | Clinical and community screening for immediate diagnosis |
| Limitations | Lower sensitivity than WHZ; some criticism regarding overall accuracy | Affected by fluid shifts; can be inaccurate if height/weight measurements are poor | Only indicates a specific type of SAM (kwashiorkor), not all cases |
| Primary Indicator | Yes, sufficient for SAM diagnosis if < 115mm | Yes, sufficient for SAM diagnosis if < -3 SD | Yes, sufficient for SAM diagnosis if present |
Integrating the Diagnostic Criteria
For a comprehensive assessment, particularly in clinical settings, healthcare providers use a combination of these methods. For instance, a child might be referred from a community screening (using MUAC or oedema) for a more detailed anthropometric assessment in a health facility (using WHZ). The WHO recommends that children with complications or a poor appetite be admitted for inpatient care, while those with uncomplicated SAM and good appetite can often be treated as outpatients, typically with ready-to-use therapeutic food (RUTF).
The Role of a Healthy Diet in SAM Prevention and Treatment
Beyond just diagnosis, a proper nutritional diet is the cornerstone of both preventing and treating SAM. This includes promoting exclusive breastfeeding, providing appropriate complementary feeding from 6 months, and ensuring access to clean water and sanitation to reduce infection risk. During treatment, a high-energy, nutrient-dense diet is crucial for catch-up growth, often involving therapeutic foods like RUTF or therapeutic milks like F-75 and F-100 for severely ill children.
Conclusion
Knowing how to calculate severe acute malnutrition is a fundamental skill for public health and clinical professionals working with vulnerable populations. By accurately applying the WHO-recommended tools—MUAC, WHZ, and bilateral pitting oedema assessment—providers can identify children at high risk and initiate life-saving interventions. This diagnostic process, paired with an effective nutrition diet, forms the basis for effective malnutrition management and ultimately, saving lives.
For more in-depth information, the World Health Organization (WHO) provides comprehensive guidance on child growth standards and malnutrition management protocols.
