Measuring acute malnutrition
In major nutritional emergencies, it may be necessary to include infants aged less than 6 months, pregnant and breastfeeding women, older children, adolescents, adults or older people in nutrition assessments or nutritional programmes.
Surveys of age groups other than children aged 6–59 months should only be undertaken if:
a thorough contextual analysis of the situation is undertaken, including an analysis of the causes of malnutrition. Only if the results of this analysis suggest that the nutritional status of young children does not reflect the nutritional status of the general population should a nutrition survey for another age group be considered
technical expertise is available to ensure a high quality of data collection, adequate analysis and correct presentation and interpretation of results
the resource and/or opportunity costs of including other age groups in a survey have been considered
- clear and well-documented objectives for the survey are formulated.
Infants under 6 months
While research is ongoing for this age group, the evidence base for assessment and management is currently limited. Most guidelines recommend the same anthropometric case definitions of acute infant malnutrition as for older children aged 6–59 months (except for mid upper arm circumference (MUAC) which is not presently recommended for infants <6 months). Admission criteria focus on current size rather than an assessment of growth. The switch from NCHS growth references to WHO 2006 growth standards results in morecases of infant <6 month wasting. The implications of this change should be considered and addressed. Potential issues include more infants presenting to feeding programmes or caregivers becoming concerned about the adequacy of exclusive breastfeeding. It is important to assess and consider:
the infants longitudinal growth – is the rate of growth good despite body size being small (some infants may for example be ‘catching up’ following low birth weight)?
infant feeding practices – is the infant exclusive breastfeeding?
clinical status – does the infant have any medical complications or conditions which are treatable or which make him/her high risk?
- maternal factors – e.g. does the mother lack family support or is she depressed? Inpatient admission to therapeutic feeding programmes should be a priority for high risk infants.
Children 6–59 months
The table below shows the commonly used indicators of different grades of malnutrition among children aged 6–59 months. Weight for height (WFH) indices should be calculated using the WHO 2006 child growth standards. The WFH Z score (according to WHO standards) is the preferred indicator for reporting anthropometric survey results.MUAC is an independent criterion for acute malnutrition and is one of the best predictors of mortality. The prevalence of low MUAC is also investigated in surveys to predict case loads for supplementary feeding and therapeutic care programmes. The cut-offs commonly used are <11.5cm for severe acute malnutrition, and 11.5–<12.5cm for moderate acute malnutrition. It is also often used, with a higher cut-off, as part of a two-stage screening process. It should not be used alone in anthropometric surveys but can be used as sole admission criteria for feeding programmes
Children aged 5–19 years
Use of the WHO 2007 growth standards is recommended to determine nutrition status in children aged 5–19 years. These growth reference data curves are a reconstruction of the 1977 NCHS/WHO reference and are closely aligned with the WHO child growth standards for children 6–59 months and the recommended cut-offs for adults. The use of MUAC in older children and adolescents, particularly in the context of HIV, may be considered. As this is a developing technical area, it is important to refer to latest guidance and technical updates.
Adults (20–59.9 years)
There is no agreed definition of acute malnutrition in adults, but evidence suggests that cut-offs for severe acute malnutrition could be lower than a body mass index (BMI) of 16 and lower than 18.5 for mild and moderate acute malnutrition. Surveys of adult malnutrition should aim to gather data on weight, height, sitting height and MUAC measurements. These data can be used to calculate BMI. BMI should be adjusted for Cormic index (the ratio of sitting height to standing height) only to make comparisons between populations. Such adjustment can substantially change the apparent prevalence of undernutrition in adults and may have important programmatic ramifications. MUAC measurements should always be taken. If immediate results are needed or resources are severely limited, surveys may be based on MUAC measurements alone.
Because the interpretation of anthropometric results is complicated by the lack of validated functional outcome data and benchmarks for determining the meaning of the result, such results must be interpreted along with detailed contextual information. Guidance on assessment can be found underReferences and further reading.
For screening individuals for nutritional care admission and discharge, criteria should include a combination of anthropometric indices, clinical signs (particularly weakness, recent weight loss) and social factors (access to food, presence of caregivers, shelter, etc.). Note that oedema in adults can be caused by a variety of reasons other than malnutrition, and clinicians should assess adult oedema to exclude other causes. Individual agencies should decide on the indicator to determine eligibility for care, taking into account the known shortcomings ofBMIandthe lack of information on MUAC and the programme implications of their use. As this is a developing technical area, it is important to refer to latest guidance and technical updates.
MUAC may be used as a screening tool for pregnant women, e.g. as a criterion for entry into a feeding programme. Given their additional nutritional needs, pregnant women may be at greater risk than other groups in the population. MUAC does not change significantly through pregnancy.MUAC <20.7cm (severe risk) and <23cm (moderate risk) have been shown to carry a risk of growth retardation of the foetus.Suggested cut-off points for risk vary by country and range from 21cm to 23cm. Less than 21cm has been suggested as an appropriate cut-off for selection of women at risk during emergencies.
There is currently no agreed definition of malnutrition in older people and yet this group may be at risk of malnutrition in emergencies. WHO suggests that the BMI thresholds for adults may be appropriate for older people aged 60–69 years and above. However, accuracy of measurement is problematic because of spinal curvature (stooping) and compression of the vertebrae. Arm span or demi-span can be used instead of height, but the multiplication factor to calculate height varies according to the population. Visual assessment is necessary. MUAC may be a useful tool for measuring malnutrition in older people but research on appropriate cut-offs is currently still in progress.
Persons with diasbilities
No guidelines currently exist for the measurement of individuals with physical disabilities and therefore they are often excluded from anthropometric surveys. Visual assessment is necessary. MUAC measurements may be misleading in cases where upper arm muscle might build up to aid mobility. There are alternatives to standard measures of height, including length, arm span, demi-span or lower leg length. It is necessary to consult the latest research to determine the most appropriate way of measuring disabled individuals for whom standard weight, height and MUAC measurement is not appropriate.