Haemoglobin and ferritin concentrations in infants at 8 months of age.

AIM To identify the optimum age to screen for iron deficiency, the normal distribution of haemoglobin and ferritin in a representative population sample was investigated. METHODS Normal values for haemoglobin and ferritin were measured from heel prick capillary samples obtained from a representative cohort of 1175 infants at 8 months old who were randomly selected from children taking part in the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC). RESULTS Haemoglobin was normally distributed: mean (SD) 117 (11) milligrams, 95% confidence interval (CI) 116 to 118, and range 72-153 milligrams. Ferritin was log normally distributed: geometric mean 38.5 micrograms/l, 95% CI 37.0 to 39.9, range 7.1-224 micrograms/l. The 5th centile for haemoglobin was 97 milligrams and for ferritin 16.9 micrograms/l. No correlation was found between haemoglobin and ferritin. Multiple regression analysis showed ferritin concentrations to be positively related to birth weight (p < 0.0001) and the sex of the child (girls with higher concentrations) (p < 0.0001) but negatively with the child's weight at 8 months (p < 0.0001). Haemoglobin concentrations were positively related to the child's weight at 8 months (p = 0.04). Neither haemoglobin nor ferritin concentrations were related to social class as measured by maternal education level. CONCLUSION These data define the normal range for haemoglobin and ferritin in capillary samples in the UK population, and suggest that anaemia is common in infancy. Using current recommendations, 23% of infants would be identified as anaemic. For British infants at 8 months of age, a more representative 'cut off' for anaemia would be haemoglobin concentration < 97 milligrams and for iron deficiency ferritin < 16 micrograms/l.