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Keith C. White, MD
PEDIATRICS Vol. 115 No. 2 February 2005, pp. 315-320
Context: Many toddlers in the United States have their hemoglobin (Hb) measured periodically. Is this worthwhile?
Objective: To determine if the presence of anemia correctly diagnoses iron deficiency (ID) and if the absence of anemia correctly rules out ID in young children.
Methodology: An analysis of data from the US National Health and Nutrition Examination Survey III (1988–1994) was performed. Subjects were children 12 to 35 months old for whom complete blood counts and cardinal measures of iron nutrition (ferritin, transferrin saturation, and free erythrocyte protoporphyrin) were reported.
Results: In the US National Health and
Nutrition Examination Survey III, the prevalence of ID ranged from 6% to 18% in
various subpopulations of toddlers. In the general population, the positive
predictive value of Hb concentration ([Hb]) <110 g/L for ID was 29% (95%
confidence interval [CI]: 20–38%), and the sensitivity was 30% (95% CI: 20–40%).
Changing the diagnostic cutoff point to [Hb] <107 g/L resulted in a positive
predictive value of 38% (95% CI: 24–52%) but lowered the sensitivity to 15% (95%
CI: 7–22%).
Conclusions: ID remains common in the
United States. In agreement with other reports, anemia in toddlers in developed
countries is more likely to be due to causes other than ID. Conversely, most
children with ID are not anemic. Many false-positive and false-negative results
render the measurement of Hb a screening test of relatively little value. The
current detection strategy needlessly treats and retests many children without
ID and leaves many iron-deficient toddlers unattended.
AUTHOR'S COMMENT FOR REUTERS HEALTH (NEW YORK), FEB 18
"For many years, anemia has been used as a proxy or synonym for iron deficiency," Dr. Keith C. White, of the University of California, Davis, told Reuters Health in an interview. "We worry about iron deficiency and iron deficiency anemia in children because they are associated with developmental problems."
"Despite considerable differences in the prevalence of iron deficiency and iron deficiency anemia, the hemoglobin test doesn't perform better for children from groups that are more affected…" Dr. White said.
"…On the other hand, a low hemoglobin only accompanies iron deficiency about one third of the time, so relying on this test overlooks two thirds of the children who are affected by iron deficiency. We know that iron deficiency and iron deficiency anemia will affect more children after their first birthday," he added. "It is wiser to try to prevent a known problem than to attempt to detect an established disease and try to cure it" research author said.