Reference intervals for serum granulocyte colony-stimulating factor levels in children

Objective: To determine age-adjusted reference intervals for children for serum granulocyte colony-stimulating factor (G-CSF) levels. Design: We determined the serum G-CSF levels of 168 disease-free children who were term neonates to 15 years of age with a highly sensitive chemiluminescent enzyme immunoassay. Results: The lowest values (5 ng/L) exceeded the detectable limit (1 ng/L) of this assay technique. The G-CSF levels were highest on the day of birth (mean +/- SD 147 +/- 146 ng/L); thereafter values decreased to 46 +/- 33 ng/L in the early neonatal period and to 23 +/- 10 ng/L in the late neonatal period. The G-CSF levels both on the day of birth and in the early neonatal period were significantly higher than in all older age groups. No significant differences were found among any of the age groups after 4 weeks of age. The G-CSF values were correlated with both blood leukocyte counts (r = 0.496, p < 0.0001) and neutrophil counts (r = 0.547, p < 0.0001). In children older than 4 weeks of age (n = 128), the 95% reference interval for G-CSF values was 5 to 42 ng/L. Conclusions: Our study in disease-free children revealed that change in serum G-CSF levels are age dependent and are correlated with neutrophil counts. Determination of reference intervals for the neonatal period requires further study.