Reference intervals for reticulocyte hemoglobin content in healthy infants.

OBJECTIVES: Iron deficiency anemia in childhood is a serious public health problem worldwide. Reticulocyte hemoglobin content (Ret-He) is a novel biomarker of iron deficiency adopted for adults but there is a lack of reference intervals for Ret-He in infants. The aim of this study was to provide data from healthy infants.

METHODS: Swedish infants (n = 456), born at term after normal pregnancies were included. Ret-He was measured at birth (umbilical cord sample), 48-72 h, 4 months, and 12 months. Reference intervals were calculated as ±2 standard deviations from the mean of Ret-He.

RESULTS: Reference intervals for newborn Ret-He were 27.4 to 36.0 pg/L (N = 376) in the cord sample, 28.1-37.7 pg/L (N = 253) at 48-72 h, 25.6-33.4 pg/L (N = 341) at four months and 24.9-34.1 pg/L (N = 288) at 12 months. Ret-He was significantly lower among iron-deficient infants, at 4 months mean difference (95% CI) -4.2 pg/L (-6.1 to -2.4) and at 12 months mean difference (95% CI) -3.4 pg/L (-5.0 to -1.8).

CONCLUSIONS: This longitudinal study presents Ret-He reference intervals based on non-anemic and non-iron-deficient infants and constitutes a step towards standardizing Ret-He as a pre-anemia biomarker of iron deficiency in children.