How does age affect neutrophil and lymphocyte counts in leukocytosis?

Updated: May 19, 2020
  • Author: Susumu Inoue, MD; Chief Editor: Jennifer Reikes Willert, MD  more...
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Always remember age-specific reference ranges for total WBC, neutrophil, and lymphocyte counts. The total WBC and neutrophil count in neonates younger than 1 week are physiologically higher than those of older children and adults. The proportion of lymphocytes and absolute lymphocyte count in children younger than 6 years are higher than those in adults. Failure to recognize age-specific lymphocytosis may lead to unnecessary investigations (see the table below for reference ranges of age-related leukocyte counts).

Infants (usually aged < 3 mo) have small storage pools of neutrophils. In severe infections, their neutrophilic demands often exceed their supplies. Therefore, young infants may have neutropenia in response to serious infection.

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