Published online November 1, 2005
PEDIATRICS
Vol. 116
No. 5
November 2005, pp.
1259
(doi:10.1542/peds.2005-1872)
Anemia Is an Important Finding and Is Likely to Respond to Iron Therapy: In Reply
Keith C. White, MD
Department of Family and Community Medicine
University of California, Davis
Sacramento, CA 95817
In Reply.—
I remain firm in my contention that, in clinical settings, the hemoglobin test is of relatively little value for screening toddlers for iron deficiency (ID).
I used a criterion standard used by the World Health Organization1 and the US Centers for Disease Control and Prevention.2 It was chosen to permit comparisons to other studies. The subject of efficient indicators of ID is the subject of a recent review.3 Although intrigued by the design of your work,4 I do not consider the results useful. In addition, to ascribe all of the transformed changes in the subjects' complete blood counts to the administration of iron is erroneous. The attribution of causality requires a control. Had your study included a suitable placebo group, meaningful inferences could have been made about the "therapeutic response."
The statistics in my study were generated as aids for practitioners to decide if it is more informative or problematic to order a measurement of hemoglobin. From the perspective of decision-making, the pretest probability of ID is rather low, as is the positive predictive value of the test, so not screening is reasonable. The prevalence of ID in children 12 to 35 months of age in the general US population is 9%. The prevalence of anemia in toddlers in the United States is 9%. If a child is anemic, the likelihood of ID increases to 28%.5 If anemia is absent, the likelihood of ID (negative predictive value) is 7% (this statistic was not reported but can be estimated easily from inspecting Fig 1 or 45). Thus, if the test is applied to 100 children, 9 will be assigned a higher risk (9% becomes 28%), and 91 will be assigned a lower risk (9% becomes 7%). Although this rearranges the estimates of hazard, it does not result in clarity.
As much as we wish for a gold standard, comparing biochemical and hematologic markers to bone marrow aspirates in a population of children will never happen. Proposing it bespeaks our want of diagnostic certainty. ID is graduated in its severity, presentation, latency, and morbidity. The best that we can hope for are instrumental truths. Half of the toddlers in the United States do not meet the recommended daily allowance for iron6 and should be considered at risk for ID. A population-based, primary prevention approach is called for. To date, evidence has suggested that screening has diverted resources to unproven efforts to detect and treat individuals who are already affected by ID.
REFERENCES
- Iron deficiency anaemia: assessment, prevention, and control—a guide for programme managers. Available at: www.who.int/nut/documents/ida_assessment_prevention_control.pdf. Accessed August 30, 2005
- Looker AC, Cogswell ME, Gunter EW. Iron deficiency—United States, 1999–2000.
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- Mei Z, Cogswell ME, Parvanta I, et al. Hemoglobin and ferritin are currently the most efficient indicators of population response to iron interventions: an analysis of nine randomized controlled trials.
J Nutr. 2005;135
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- 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
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- White KC. Anemia is a poor predictor of iron deficiency among toddlers in the United States: for heme the bell tolls.
Pediatrics. 2005;115
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–320[Abstract/Free Full Text]
- United States Department of Agriculture. 1994–96 Continuing Survey of Food Intakes by Individuals table set 12: supplementary data tables. Available at: www.ars.usda.gov/SP2UserFiles/Place/12355000/pdf/Supp.PDF. Accessed August 30, 2005
PEDIATRICS (ISSN 1098-4275). ©2005 by the American Academy of Pediatrics
