There is a lot to question in the AAP statement about supplementing with iron before 6 months, including four out of five of Karen Gromada's post and the issue of premature cord clamping and the issue of increasing prematurity because of scheduled surgical deliveries and perhaps most importantly the rampant use of formula in the early days of life.  I mistrust much of the data on exclusivity because of how mothers respond to me when I ask about supplementation.  It takes careful questionning to find out that the baby had been given "just a little" because mom slept and it doesn't take into account mom's insisting that their baby was always brought to them at night when they slept for five to six hours.  

The use of formula, with its much higher level of iron in order to compensate for poor absorption, is entirely likely to throw off the absorption of iron from breast milk.  We know from many studies that absorption of iron does change depending on the diet. 

So, if anyone has a copy of the November Pediatrics article (which I cannot get from the AAP website despite their claim that this ha already been published online) I would really like to read the full version article to figure out what data they actually looked at to reduce the age to four months.

Second, I'm going to try again to explain why hemoglobin is NOT an indicator of iron sufficiency.

Problem number 1:  Construct validity
Hemoblogin does NOT measure iron stores.  It measures anemia.  Anemia can be due to lack of iron in the diet, lack of vitamin B12 in the diet, hereditary conditions such as thalassemias, infections, and parasites.  At higher altitude, the hemoglobin is elevated -- so that more individuals woudl be anemic and show up with "normal" hemoglobin values.  So, one can reach a false conclusion than an individual is IRON deficient due to relying only on hemoglobin.


Problem number 2:  Measurement errors.
If hemoglobin is measured with a finger or heel stick, which is commonly done with infants and young children it is more prone to measurement error.  I spent about three years working with the HemoCue machine that is used widely in Manhattan pediatric offices and there are many ways to throw a value off.  The machine can be miscalibrated, the finger can be squeezed too tightly, the finger can be milked, the cuvette may not be fully filled, etc.  On a population level, this can lead to characterizing a population as having a higher prevalence of anemia than is actually the case because measurement error spreads the curve.  For this reason, the International Nutritional Anemia Consultative Group found bitterly against using the HemoCue for programs.  They forgot, however, that it is perfectly fine if you are trying to see if an intervention decreased anemia in the population -- whereby your measurement error would be the same in your before and after studies.  On an individual level, however, this measurement error becomes much more important.  It means that INDIVIDUALS may be misdiagnosed.

Problem number 3:  Classification
The cutoff values for hemoglobin do not always predict who is truly anemic.  It was well known when I was a graduate student that if you relied on hemoglobin alone, you would have a subset of those classified who did not respond to iron supplementation.  In fact, many of these individuals were perfectly fine iron stores.  Similarly, you can have individuals who are below that cutoff who really do need additional iron.  This problem can be exaggerated by problem 2 because measurement error tends to widen the curves in a population -- eg. more falsely high values and falsely low values ending up with more misdiagnoses. We talked about "responders" and "nonresponders" with the "nonresponders" being those who did not need the iron.

Problem number 4: Prevention versus Treament
With something as important as cognitive development, you would really want to PREVENT any damage from occurring.  Just as we would like to PREVENT true failure to thrive.  Neither hemoglobin not weight gain are helpful for preventing the condition from occurring.  Or to give another example of famine.  You don't want to use the percentage of malnourished children in your population as the indicator to prevent famine.  By the time these conditions occur, it is too late.  The damage is done.  We know that in Indonesia, rice prices were a good early predictor of potential famine -- leaving enough time to take corrective measures to prevent the famine.  In other countries other indicators might be chosen.  In the case of failure to thrive -- better indicators would be the rhythmicity of a baby's swallowing and the behavior before, during and after feeding.  If a baby is swallowing well and the behavior suggests satisfaction compared to the baby that is not swallowing and either lethargic or acting hungry -- you can take measure that prevent the failure to thrive that might lead to supplementation (such as more skin to skin, breast switching, breast compressions -- etc).

By the time the baby is anemic, the stores are gone, the iron deficiency has been there, the cognition has already been impacted.  So, our dilemma here is that we don't have great early term indicators.  The other tests for iron stores are highly invasive.  

This is why the sloppiness of some of the research on iron deficiency is important to clear up.  This is why I want to read those original articles.  This is why issues such as the unreported use of formula, premature cord clamping, scheduled surgical deliveries are very important for public health policy.  

Best, Susan Burger

 

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