Purpose: This study tested the adequacy of established leukocyte indices in infants < or = 1,200 gm birth weight and < or = 32 weeks gestation.
Design: Charts of all admissions to the NICU from March 1991 through September 1994 were retrospectively reviewed.
Sample: All infants (n = 131) were outborn and admitted to the NICU within 24 hours after birth.
Main outcome variable: The leukocyte indices obtained during the first 72 hours after birth were plotted as a function of time in hours.
Results: Mode of delivery significantly affected total leukocyte count and absolute neutrophil count; sex and use of prenatal steroids did not. Ranges for total leukocyte count, absolute neutrophil count, and immature/total neutrophil (I:T) ratio demonstrate that normal values are variable and change over time. PRACTICE RECOMMENDATIONS: The wide distribution of values found, coupled with differences noted by mode of delivery, make normative data difficult to apply. The clinician must question the appropriateness of routinely obtaining a complete blood count and the clinical utility of the results.