Haemoglobin and ferritin concentrations in children aged 12 and 18 months

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Abstract
AIMS To define the normal ranges and investigate associated factors for haemoglobin and ferritin in British children at 12 and 18 months of age, and to estimate correlations between both haemoglobin and ferritin concentrations at 8, 12, and 18 months of age. SUBJECTS AND METHODS Subjects were part of the “children in focus” sample, randomly selected from the Avon longitudinal study of pregnancy and childhood. Capillary blood samples were taken from 940 children at 12 months and 827 children at 18 months of age. RESULTS Haemoglobin was distributed normally and ferritin was distributed log normally at 12 and 18 months of age. Ninety five per cent reference ranges were established from empirical centiles of haemoglobin and ferritin. Haemoglobin concentrations at 18 months were associated with sex and maternal education. Concentrations of ferritin at 12 and 18 months of age were associated with birth weight and current weight. Girls at 12 months, but not at 18 months, had 8% higher ferritin concentrations than boys. Haemoglobin and ferritin concentrations were significantly correlated over time (8–12 months:r Hb = 0.26,r Fer = 0.46; 12–18 months:r Hb = 0.37,r Fer = 0.34; 8–18 months:r Hb = 0.22,r Fer = 0.24). CONCLUSION Iron stores are depleted by rapid growth in infancy. A definition of anaemia based on the fifth centile gives cut off points at 12 and 18 months of age of haemoglobin < 100 g/l, and for iron deficiency of ferritin < 16 μg/l and < 12 μg/l, respectively. Because children below the fifth centile at one time point differ from those six months later, it is unclear whether screening would be effective.