Anaemia doesn't predict iron deficiency among toddlers
BMJ 2005; 331 doi: https://doi.org/10.1136/bmj.331.7507.0-f (Published 30 June 2005) Cite this as: BMJ 2005;331:0-fAll rapid responses
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The concept that the response to a therapeutic trial might be a
decisive diagnostic aid(1) is one that deserves greater recognition, given
the fact that it is applicable to a wide variety of disciplines.
For, example, the cost-effectiveness of establishing the diagnosis of left
ventricular(LV) diastolic failure would be considerably enhanced if, for
non-research purposes, instead of a reliance on "evidence of abnormal left
ventricular relaxation, filling, diastolic distensibility or diastolic
stiffness"(2)when evaluating patients in whom suspected LV failure co-
existed with normal LV ejection fraction, recourse was made to the
clinical and, especially, radiographic response to antifailure therapy,
the radiographic parameters being those recently validated as being highly
predictive of LV failure(3).
Yours sincerely
OMP Jolobe
References
(1) Wright CM., Kelly J., Trail A., Parkinson KN., Summerfield G
The diagnosis of borderline iron deficiency:results of a therapeutic trial
Archives of Disease in Childhood 2004:89:1028-31
(2)European Study Group on Diastolic Heart Failure
How to diagnose diastolic heart failure
European Heart Journal 1998:19:990-1003
(3) Knudsen C., Omland T., Clopton P et al
Diagnostic value of B-Type Natriuretic Peptide and Chest Radiographic
Findings in Patients with Acute Dyspnoea
American Journal of Medicine 2004:116:363-8
Competing interests:
None declared
Competing interests: No competing interests
I am grateful to Oscar Jolobe for drawing attention to our recent
study (1) which was published after the Pediatrics paper (2) was accepted
for publication.
Ours was a before and after intervention study in contrast to the
Pediatrics study, which although classified by the authors of the POEM as
a trial, was in fact simply a cross sectional cohort study.
We also found only a modest overlap between anaemia and iron
deficiency, but to our surprise both total and mean cell haemoglobin
proved powerful predictors of a therapeutic response to iron. Unless
supposed markers of iron deficiency are tested against a therapeutic
response, all that is really being demonstrated is how poorly most of them
actually function as indicators of iron deficiency.
Reference List
1. Wright CM, Kelly J, Trail A, Parkinson KN, Summerfield G. The diagnosis
of borderline iron deficiency: results of a therapeutic trial.
Arch.Dis.Child 2004;89:1028-31.
2. White KC. Anemia is a poor predictor of iron deficiency among toddlers
in the United States: for heme the bell tolls. Pediatrics 2005;115:315-20.
Competing interests:
I am the first author on a research study that drew precisely opposite conclusions
Competing interests: No competing interests
If anaemia is an insensitive marker of iron deficiency(1)(2), which
of the other commonly used red blood cell(RBC) indices is best able to
identify iron deficiency in at risk non-anaemic subjects?
A tentative answer to this question came from a study in which 462
toddlers were screened, and, among them 60 proved to be iron deficient.
Within the latter group, even in isolation(ie even in the absence of
anaemia or mean cell volume below the screening threshold level of 75 fl),
a mean cell haemoglobin(MCH) of < 25 pg proved capable of identifying
the presence of iron deficiency, whilst an MCV of < 75 fl, on its own,
did not appear to be associated with iron deficiency in non-anaemic
subjects(2).
A more convincing way of comparing the predictive value of the two RBC
indices would be to target, for the purpose of study, non-anaemic subjects
derived from a population at high risk of iron deficiency, such as
toddlers being weaned on low iron content feeds or those being fed almost
exclusively on unmodified cow's milk(3), or toddlers of South Asian
origin(4). The question is one worth addressing, given the fact that, even
in the absence of anaemia, iron deficiency is capable of causing
neurodevelopmental abnormalities(5).
Yours sincerely
OMP Jolobe MRCP(UK)
Refernces
(1)White K
Anemia is a poor predictor of iron deficiency among toddlers in the United
States
Pediatrics 2005:315-20
(2) Wright CM., Kelly J., Trail A., Parkinson KN., Summerfield G
The diagnosis of borderline iron deficiency:results of a therapeutic trial
Archives of Disease in Childhood 2004:89:1028-31
(3) Daly A., MacDonald A., Aukett A ., et al
Prevention of anaemia in inner city toddlers by an iron supplemented cow's
milk formula
Archives of Disease in Childhood 1996:75:9-16
(4)May R., Aukett A
Population screening for anaemia in the inner city
Ambulatory Child Health 2000:6:8-11
(5) Walter T., Kovalskys J., Stekel A
Effect of mild iron deficiency on infant mental development scores
Journal of Pediatrics 1983:102:519-22
Competing interests:
None declared
Competing interests: No competing interests
Dear Sir,
I was most interested to read the POEMS report on the lack of
sensitivity and specificity of anaemia for iron deficiency in children. I
was a little alarmed at the suggestion that SERUM haemoglobin levels are
used to screen for anaemia - the normal PLASMA haemoglobin level is on the
order of 15,000 times lower than the BLOOD haemoglobin level, which of
course is the parameter usually measured for screening for anaemia.
Yours,
Competing interests:
None declared
Competing interests: No competing interests
Bottom line
Forgive me if I am being obtuse, but the paragraph entitled "bottom
Line" seems to contain a couple of misleading statements: while it is
unsurprising that we cannot assume iron stores are always reflected by
haemoglobin levels, it is perplexing to hear that haemoglobin itself is
being branded an unreliable marker of anaemia. Presumably this was a
typing error? Thank you.
Competing interests:
None declared
Competing interests: No competing interests