Differences in Total White Blood Cell Counts and Absolute Neutrophil Counts between Very Low Birth Weight African American and Caucasian Neonates

Abstract 1544 Poster Session II, Sunday, 5/2 (poster 129)

It has been shown that total white blood cell counts (WBC) and absolute neutrophil counts (ANC) are lower in African American (AA) than in Caucasian (CC) adults and children. To date, racial differences in the complete blood counts (CBC) of very low birthweight (VLBW) infants have not been examined.

Objective: examine hematologic parameters in AA and CC VLBW neonates during the first 72 hours of life. Methods: retrospective analysis of CBC results on admission and at 24, 48 and 72 hours of life from all AA and CC VLBW neonates admitted to a single level III nursery from 7/93 to 7/97. Infants were included only if a CBC was collected at all study points (Caucasion n=140, African American n=120). Repeated measures ANOVA was used to compare the two groups. Covariates controlled for included GA, IUGR, maternal age, Apgar scores, delivery method, artificial ventilation, PROM, chorioamnioninitis, sepsis, PIH, maternal steroids and MgSO4 therapy. Hematocrit data were also corrected for number of transfusions. Post hoc testing was performed using the least significant difference test. Neutropenia was defined as ANC< 1750/mm³. Data are expressed as a mean ± SD, a p value <.05 was considered significant. Results: overall, AA VLBW infants had higher total WBC (p<.01) and ANC (p<.01), and lower hematocrits (p<.03) in the first 72 hours of life compared to CC infants. When specific time points were examined, there was no significant difference in total WBC on admission (p=0.38). However, AA neonates had higher total WBC counts at 24hrs (AA 15.9 ± 14.6, CC 13.6 ± 10.1/mm³, p<.01), 48hrs (AA 15.5 ± 15, CC 12.1 ± 10/mm³, p<.01), and 72hrs (AA 14.8 ± 13.6, CC 11.0 ± 9.3/mm³, p<.01) when compared to CC neonates. There was no significant difference in ANC on admission and at 24hrs, but ANC was significantly higher in AA neonates than in CC neonates at 48hrs (AA 9.5 ± 11.3, CC 7.3 ± 7.5/mm³, p<.0002) and 72hrs (AA 8.0 ± 9.4, CC 5.5 ± 6.3/mm³, p<.01). However, CC infants were not more likely to be neutropenic (38%) than AA infants (33%, p=.37) during the 1st 72 hours of life. Hematocrit on admission (CC 45 ± 7.4, AA 42 ± 6.0%, p<.01) and 24hrs (CC 45 ± 15.8, AA 40 ± 7.4%, p<.01) was significantly lower in AA than in CC neonates. No significant differences were seen at 48 or 72 hours. No significant differences were found for platelet counts or nucleated red blood cell count at any of the study time points. Conclusions: in contrast to adults and children, we have found that AA VLBW neonates have higher total WBC counts and ANC than CC VLBW neonates in the first 72 hours of life. We also have shown that the hematocrit is significantly lower in AA VLBW neonates on the day of birth and the first 24 hours than in CC VLBW neonates.

Further study will be needed to explore the clinical significance of these findings.