There is a range of data collection methods.  Table 1 outlines some of the most common ways of collecting data in emergencies.

The assessment of nutritional status is based on simple anthropometric data and limited to children of preschool age, who serve to represent the general population.  Generally, the data collected are weight, height, sex, edema, and age (if available).

The assessment is limited to protein-energy malnutrition without attempting to assess other nutritional deficiencies.  No further variables should be added without considering the additional workload and delay involved.

Weight for height is recommended as the main or only indicator of malnutrition by most manuals and guidelines issued by UN agencies, governments, and nongovernmental organizations.  It is robust, is independent of age for children, has an internationally accepted reference population, and its interpretation is based on wide experience in many parts of the world.  The indicator is formed from weight and height measurements by comparing the weight of each child to the distribution of weights of reference children of the same height.  Boys and girls are treated separately, although in the field a quick analysis can be done using a table for combined sexes.

Height and weight are measured by practical techniques that are mentioned in various manuals (2-9).  An assessment of the ages of children is important for two reasons:  1) malnutrition is often most marked between 6 and 18 months, which is why the age groups below and above 2 years of age should be considered separately for relief action; 2) if the height of older children is measured when they are standing, the dividing line is 2 years.  If age is uncertain, no effort should be made to estimate it.  Instead, lengths and heights should be used to group children by approximate age equivalents.

Body measurements are required for objective assessment of nutritional status and comparison with regular surveillance data.  Weight-for-Height (Weight-for-Length). The weight-for-height (weight-for-length) method, which is expressed either as a percentage of a reference median or as a Z-Score, is preferred for nutritional surveillance and for measuring individual progress in emergencies. If a percentage is used, it indicates the weight of the child expressed as a percentage of that of a well-nourished child of the

Table 1.  Common nutrition status data collection methods

Method	Description
Automatic initial self and local assessment	This can involve assessments conducted by staff of “lifeline” systems and can involve preplanned damage reporting by civil authorities and by military units.
Visual inspection and interviews	Methods can include actions by special point assessment teams (including preplanned visits), and sample surveys to achieve rapid appraisal of area damage.
Sample surveying of specific characteristics of affected populations	The choice of sampling method depends mainly upon practical conditions.  In settlements and camps, systematic random sampling is the method of choice; in a scattered population cluster sampling may have to be the choice.  It must be kept in mind that in cluster sampling the sample size needs to be twice that of systematic random sampling. If an estimate of malnutrition is needed for a relatively small group of children, it is best to examine all of them.  In a small population (200-3000 people) of those 18-20% may be children below 5 years of age (400-500) – all eligible children should be examined.  In larger populations it is usually easier to examine only a sample of children and to draw conclusions on the probable proportion of malnourished children in the total population.  There are several different types of sample surveys: -        Simple random sampling: every member of the target population is equally likely to be selected, and the selection of a particular member of the target population has no effect on the other selections. -        Systematic random sampling: every fifth, or tenth, member on a numbered list is chosen (may be wildly inaccurate if the lists are structured in certain ways). -        Stratified random sampling: the population is divided into categories (or strata); members from each category are then selected by simple or systematic random sampling; then combined to give an overall sample. -         Cluster sampling: the sample is restricted to a limited number of geographical areas, known as "clusters"; for each of the geographical areas chosen, a sample is selected by simple or random sampling. Subsamples are then combined to get an overall sample.
"Sentinel" surveillance	This is a method used widely in emergency health monitoring, where professional staff establish a reporting system that detects early signs of particular problems at specific sites. The method can be applied where early warning is particularly important.
Detailed critical sector assessments by specialist	This involves technical inspections and assessments by experts. It is required in sectors such as health and nutrition, food, water supply, electric power, and other infrastructure systems in particular.
Continuing surveillance by regular "polling" visits	This technique is well developed in epidemiological surveillance of casualty care requirements and emergent health problems.
Continuing surveillance by routine reporting	As the situation develops, it is especially useful if routine reporting systems can be adapted and used to develop a comprehensive picture of events.
Interviews with key informants	Interviews with key informants in government and PVO/NGO/IOs and within particular groups of affected people, local officials, local community leaders, and (especially in food and displacement emergencies) with leaders of groups of displaced people.

same height as given in international reference tables. If a Z-Score is used, the "Z" represents the median for children and a Z-Score represents the number of standard deviations above or below the median (since the population is normally distributed, the median equals the population mean). Children with less than 80 percent weight-for-height or with a Z-Score of less than -2 are classified as malnourished; those with less than 70 percent weight-for-height or with a Z-Score of less than -3 are considered severely malnourished. Without special feeding programs, severely malnourished children will die.

Mid-Upper-Arm Circumference (MUAC). Another method used when a rapid screening of young children is necessary is the mid-upper-arm circumference (MUAC) measurement. It is less sensitive than the weight-for-height method but can be done more quickly. It measures the part of the arm whose circumference does not normally change significantly between the ages of 1 and 5, but which wastes rapidly with malnutrition. The technique is not suitable for monitoring the progress of individual children. Professional help should be used for the arm circumference method.  Before being measured, the child should be checked for edema, the swelling associated with kwashiorkor.

Edema is the presence of abnormally large amounts of fluid in the intercellular tissue.  It is the key clinical sign of a severe form of protein-energy malnutrition carrying a very high mortality rate in young children.  Cases with edema are separated from the rest during the analysis and are counted as severe malnutrition.  A prevalence of edema of 1 or 2% is a sign of widespread malnutrition.  In some circumstances recording of dehydration may be indicated.  This may be important where diarrhea disease plays a major role and may especially affect children with evidence of wasting.

Various field guides have suggestions on data recording and forms, training and supervision, data analysis and interpretation, and reporting (format) of findings.  They also include examples of sampling, normalized reference tables of weigh-for-height, etc.