Prevalence of Global Acute Malnutrition (GAM) Based on WHZ

Impact

% of children aged 6–59 months with WHZ < −2 and/or bilateral pitting oedema

The indicator measures the prevalence of global acute malnutrition (GAM) based on Weight-for-Height Z-score (WHZ) among children aged 6–59 months: WHZ < −2 and/or bilateral pitting oedema. Moderate wasting based on WHZ is defined as WHZ ≥ −3 and < −2 without bilateral pitting oedema. Severe acute malnutrition based on WHZ and/or oedema is defined as WHZ < −3 and/or bilateral pitting oedema.

Collect the data through a probability-based anthropometric survey that is representative of the population and geographic area for which the prevalence estimate will be reported. Data can be collected as part of a SMART survey or through another appropriately designed survey that meets recognised anthropometric sampling and data-quality standards.

For each selected child aged 6–59 months, measure weight and recumbent length or standing height in accordance with SMART/WHO anthropometric procedures and assess bilateral pitting oedema using the standard technique on both feet. Enumerators should receive practical training and undergo standardisation before data collection.

Calculate Weight-for-Height Z-score (WHZ) using the 2006 WHO Child Growth Standards. Calculate the indicator by dividing the number of surveyed children aged 6–59 months with WHZ < −2 and/or bilateral pitting oedema by the total number of surveyed children aged 6–59 months included in the anthropometric analysis. Children meeting both criteria must be counted only once. Multiply the result by 100 to express it as a percentage. Report the result with a 95% confidence interval and account for the survey design, including clustering and sampling weights where relevant. Check anthropometric data quality using SMART guidance.

This data can be disaggregated by sex, age group and geographic area.

1) For humanitarian severity analysis, IPC classifies GAM based on the Weight-for-Height Z-score (WHZ) as: <5% Acceptable; 5.0–9.9% Alert; 10.0–14.9% Serious; 15.0–29.9% Critical; and ≥30% Extremely Critical. These thresholds apply to GAM based on WHZ, including bilateral pitting oedema. WHO uses different public-health significance categories for wasting based on WHZ < −2 without oedema, so these should not be substituted for the IPC GAM thresholds.

 

2) This indicator requires reliable identification of whether a child is aged 6–59 months. Exact age in months is also important for age disaggregation, data-quality checks and determining the appropriate length/height measurement procedure, but WHZ itself is based on weight, length/height and sex rather than age. Whenever possible, verify the child’s age using a birth certificate, vaccination card or another reliable document. If such documents are unavailable or their accuracy is uncertain, use a locally adapted events calendar to help estimate the child’s age (see FAO guidance below).

  

3) Always follow the relevant Ministry of Health procedures for anthropometric surveys, including approval and reporting requirements. For this indicator, calculate WHZ using the 2006 WHO Child Growth Standards. If national requirements also request results using another growth reference, report these separately and do not mix them with the WHO-standard series.

  

4) Prevention-oriented projects should use this indicator only if their strategy is likely to have an impact on the nutritional status of the target population. If your project is too short or focuses, for example, primarily on improving agricultural production, use less ambitious indicators measuring, for example, nutritional intake (such as Minimum Dietary Diversity) or specific nutritional practices.

  

5) In many countries, acute malnutrition is prone to significant seasonal differences (e.g. ranging from 5% in the months following the harvest to 11% prior to the harvest). Therefore, if you need to compare your baseline and endline data to assess the result of your work, ensure that the data is collected at the same time of a year, otherwise you will receive two sets of data which say very little about the change your project has (not) achieved.

  

6) Determine the required sample size from the expected prevalence, desired absolute precision, survey design effect, anticipated non-response and intended use of the results. SMART considers approximately ±3 percentage points sufficient for many GAM surveys, while requiring substantially narrower confidence intervals can result in unnecessarily large samples. Training and fieldwork duration should likewise be determined by the survey design and the team’s demonstrated competence. Training must include practical anthropometric measurement, oedema assessment, piloting and standardisation, with further practice or retraining where performance is inadequate. If the team does not have sufficient experience in SMART surveys, engage an experienced adviser to support survey design, training and quality assurance.

7) Establish a referral procedure before starting data collection. Children identified with bilateral pitting oedema or severe wasting during the survey should be referred in accordance with national protocols for prompt assessment and appropriate care.

8) Always report this result as GAM based on WHZ. Do not assume that it is interchangeable with GAM based on MUAC. WHZ and MUAC identify overlapping but different groups of children.

    

Also consider using the following indicators:

• Prevalence of Global Acute Malnutrition (GAM) Based on MUAC (provides the complementary MUAC-based estimate while avoiding the assumption that MUAC and WHZ prevalence are interchangeable)

• Coverage of Acute Malnutrition Treatment Services (links the measured population burden of acute malnutrition with access to treatment)