Haemoglobin and red blood cell reference intervals during infancy.

OBJECTIVES

There is a need for updated haematological reference data in infancy. This study aimed to define intervals for haemoglobin and red blood cell biomarkers based on data from a large cohort of longitudinally followed Swedish infants.

DESIGN

Longitudinal cohort study.

SETTING

Two Swedish study centres.

PARTICIPANTS

Three community-based populations including 442 presumably healthy infants born at term and with umbilical cord clamping delayed to 30 s or more after birth.

METHODS

Blood samples were collected from umbilical cord blood (a), at 48-118 hours (b), at 4 months (c) and at 12 months (d). Reference intervals as the 2.5th and 97.5th percentiles were calculated in coherence with Clinical and Laboratory Standards Institute guidelines.

RESULTS

Reference intervals for haemoglobin (g/L) were: (a) 116-189, (b) 147-218, (c) 99-130, (d) 104-134, and for mean cell volume (fL): (a) 97-118, (b) 91-107, (c) 71-85, (d) 70-83. Reference intervals for erythrocyte counts, reticulocyte counts, reticulocyte haemoglobin, mean cell haemoglobin and mean cell haemoglobin concentration were also estimated. According to the WHO definition of anaemia, a haemoglobin value less than 110 g/L, 16% of this presumably healthy cohort could be classified as anaemic at 12 months.

CONCLUSION

We found mainly narrower reference intervals compared with previously published studies. The reference intervals for each parameter varied according to the infants' age, demonstrating the necessity of age definitions when presenting infant reference intervals. The discrepancy with the WHO classification for anaemia at 12 months, despite favourable conditions in infancy, needs future investigation.