Screening test for infant iron deficiency

A new blood test detects iron deficiency in infants earlier and more accurately than the commonly used haemoglobin screening test, according to a study in the August 24/31 issue of the Journal of the American Medical Association. Iron deficiency is estimated to affect nearly 10% of American children one to two years of age. Early detection and treatment are critical because iron deficiency can impair infant mental development, possibly permanently, even before it progresses to anaemia.

The study, done at Children's Hospital Boston, is the first to compare a new test called CHr with the standard haemoglobin test as a screen for iron deficiency in infants. The CHr test measures the haemoglobin content of reticulocytes, or immature red blood cells, whereas the standard haemoglobin test is based on the entire population of red blood cells. Because reticulocytes are present in the bloodstream for only 24 to 48 hours, as compared with several months for mature red blood cells, measuring the reticulocyte haemoglobin content (ie, CHr) provides a more timely indication of iron status, the investigators say.

In this study, 200 healthy infants 9 to 12 months of age underwent both tests, as well as a transferrin saturation test, which is the 'gold standard' test for iron deficiency but is impractical for routine screening. Using the optimal CHr cutoff value (established as 27.5 pg), CHr correctly identified 83% of the iron-deficient infants, compared with only 26% identified by the current screening standard (a haemoglobin level less than 11 g/dL.