0928 Severe acute malnutrition rates using NCHS vs WHO growth standards

It is common to read articles that open with statements such as “Severe acute malnutrition affects 13 million children globally and causes 1 to 2 million child deaths every year.” More recently, aid agencies have reported an increase to 19 million affected. This 16% increase would typically be ascribed to climate changes (especially drought), civil unrest, and food shortages and poverty levels related to the recent and continuing global financial meltdown that has affected prices, supply chains and adequacy of healthcare systems. But what of the measurement tools and changes that are taking place in the use of NCHS growth standards vs those recommended by WHO? We are used to seeing various rates changing as input factors are changed e.g. national unemployment rates vary dramatically depending on how one defines employment or measures the number of active work-seekers, and inflation rates vary according to what is in the ‘basket’ and how each component is weighted or re-weighted from time to time. WHO growth standards are currently regarded as an international reference for describing how children should grow when measured by height and weight. Previously, severe acute malnutrition (SAM) was defined as weight for height <70% or < -3 Z scores below the NCHS median. The new case definition is weight for height < -3 Z scores below the WHO growth standards median. Simply changing from NCHS to WHO changes a national SAM rate: for countries that previously used the definition of <70% of NCHS median a change to < -3 Z scores (WHO) may produce a dramatic SAM increase (8-fold in one study), or a smaller increase when switching from NCHS < -3 Z scores to WHO < -3 Z scores. A global figure for SAM rate is obviously going to depend on how SAM is measured around the world, and what is now recognized is that there are differences in how that is being done. High rates demand interventions that require money as well as supply and distribution chains, and rising SAM rates would (perhaps erroneously, as per above) suggest that systems are failing or the problem escalating. Under these circumstances it is probably unwise to get too deeply into the dilemma of not being able to see the wood for the trees. Whichever system one is using, rather attempt to identify those children who are at higher risk and focus attention on them as they might benefit most from treatment.

Read more:
Lancet 2009; 374: 100-102
WHO 2006. http://www.who.int/childgrowth/standards/en
Pediatrics 2009,; 123: e54-9