15 October 2014

Telegram SAM: Children of the Nutrition Data Revolution

For those of you too young to get the T-Rex reference, this is a post to highlight a great blog by Andre Briend that may have gotten lost in the summer holidays.  

Andre reminds us that many children with Severe Acute Malnutrition (SAM), as defined by the UN, may be omitted from current prevalence estimates. 

SAM is defined by WHO and UNICEF by a weight-for-height index (WHZ) less than -3 z-score OR a mid-upper arm circumference (MUAC) less than 115 mm OR presence of oedema (significant observable swelling due to fluid accumulation).  In other words if any one of those 3 conditions holds, then the child is severely acutely malnourished.  

So what's the problem?  Well current estimates of children under 5 suffering from SAM are based on prevalence surveys counting children with a WHZ less than -3 z-score.   In other words, if a child has WHZ greater than -3 but has low MUAC or oedema, then the child is not classified as SAM when they should be--so the estimate based purely on WHZ less than -3 is a lower bound.    

So how big an underestimate of SAM do we get from relying solely on WHZ less than -3?  Well, Andre cites studies showing factors of discrepancy from 1.6 to 8!  

I'm not an expert, but I would imagine measuring MUAC is easier than measuring oedema.  Can we not have a few Demographic and Health Surveys that assess MUAC in addition to the usual WHZ so we can get an idea of how badly we are getting it wrong?

More of the world's children need to benefit from a nutrition data revolution. The Global Nutrition Report has a whole chapter devoted to this.   

1 comment:

Mahamadou Tanimoune said...

Dear Lawrence,
Thank you very much for raising this issue. I think that the MUAC time came now. As you mentionned the MUAC is easier measure but is subject to many criticism maybe subjective.
in 2008 when preparing my master thesis I work on the use of the MUAC in the food security system. Based on my report (http://www.cilss.bf/nusapps/pdf/memoirevf.pdf) I have been selected for oral communication the ISS 2012 FAO.
after reading more than 70 papers old and recent on the use of MUAC I found some contradiction in the criticism: both say the link with mortality and easiness and in contrary the accuracy limited where we all know that the systematic measurement error is one in MUAC and fro WH you face the weight and height one. in any case the height is more complicated to measure than the MUAC even with low level of education. So if you have something please to go through the link above for my report there some argument that my help to advocate for the MUAC consideration in Survey.