Red blood cell distribution width: reference intervals for neonates

Abstract

Objective: To create reference intervals for red blood cell distribution width (RDW) of neonates and to use these intervals to better understand and classify hematopathology of neonates.

Study design: This was a retrospective analysis of data from neonates born between 1/1/2001 and 12/31/2011, who had a complete blood cell count (CBC) in the first 14 days. The first RDW recorded from each was displayed according to gestational and postnatal age. Correlation between RDW and reticulocyte count was sought when the two tests were obtained simultaneously. Focused studies were performed on the 20 neonates with the highest and the 10 with the lowest RDW values.

Results: RDW values from 165 613 CBCs were included. RDW reference intervals for neonates are higher than for older children and adults. At birth, the lower reference limit for term and late preterm neonates is 15.5%. The upper reference limit is 20%, and is slightly higher (up to 23%) in preterm neonates. For term and late preterm neonates the range does not change in the first two weeks but preterm neonates have a rise in upper reference limit concordant with erythrocyte transfusions. RDW and reticulocytes correlated positively but weakly (r²= 0.187). Eighteen of the 20 with the highest RDW values (29.4–42.8%) at birth had anemia with prenatal hemorrhage or hemolysis. Those with the lowest RDW values (11.8–13.7%) at birth tended to have a low MCV for age (95.5 ± 11.4 fL versus.129.8 ± 19.3 fL with a high RDW, p < 0.00001).

Conclusion: The RDW reference interval at birth is 15.5–20% and does not change appreciably over the first two weeks except for those receiving a transfusion where the RDW increases. High RDW values at birth indicate anisocytosis commonly due to macrocytic reticulocytosis; low values correlate with relative microcytosis.

• Anemia
• erythrocyte
• hematocrit
• RBC indices
• RDW
• red cell distribution width

Acknowledgements

We thank Ian Giles, MD, Director of Medical Affairs, Sysmex America, Inc., for reviewing the manuscript and for helpful discussions on neonatal hematology and hematological reference intervals for newborn infants.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.