The aim of this study was conducted to investigate the mean nRBC count in very low births weight infants (VLBWIs) and to determine the usefulness of the nRBC as an independent prognostic factors of perinatal complications in VLBWIs.
This study was conducted on 112 VLBWIs who were hospitalized in the neonatal intensive care unit (NICU) of the author's hospital within the period from March 2003 to and May 2008. Based on the infants' nucleated red blood cells (nRBC) counts at birth, on the third day after birth, on the seventh day after birth, in the second week after birth, and in the fourth week after birth in the medical records, the correlation between nRBC or absolute nRBC counts with birth weight, gestational age, and other perinatal outcomes were retrospectively investigated.
In VLBWIs, their mean nRBC and absolute nRBC counts were showing a gradual decrease after birth, and they were consisteantly kept at low values since one week after and inversely proportional to the birth weights. The mean nRBC counts based on the stage after birth showed a significant correlation with perinatal death, necrotizing enterocolitis, and severe intraventricular hemorrhage.
The increase in the nRBC count showed a significant correlation with having a severe intraventricular hemorrhage, necrotizing enterocolitis, and perinatal death in VLBWIs. If an increase or no decrease in the nRBC count after birth is observed, newborn-infant care precautions should be required.
Factors predicting harmful perinatal complications have been an issue along with the improved prematurity survival. Nucleated red blood cell (nRBC), a premature red blood cell, is an indicator of hematopoiesis in a newborn infant and has been known to be associated with intrauterine hypoxia
As a method that describes nRBC, the nRBC count is measured per 100 white blood cells (WBC). The maximal 30/100 WBC can be observed at a gestational age of less than 30 weeks with a physiologically high extramedullary hematosis. After that, the count returns to the normal 5-10/100 WBC
This study was conducted in a total of 126 very low birth weight infants (VLBWIs) at birth and who were hospitalized in the neonatal intensive care unit (NICU) of Konyang University Hospital within the period from March 2003 to May 2008. Infants with congenital anomalies, chromosomal abnormalities, twin-to-twin transfusion, expected death within 48 hours after birth, and severe anemia were excluded. Based on their nRBC counts at birth, on the third day after birth, on the seventh day after birth, in the second week after birth, and in the fourth week after birth reflected in the medical records, the correlation between the nRBC or absolute nRBC counts with birth weight, gestational age, 5-min Apgar score, small for gestational age (SGA), hyaline membrane disease (HMD), bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH), pulmonary hemorrhage, and death after birth were retrospectively investigated.
The gestational age was calculated starting from the first day of the mother's last menstruation, and was confirmed through the physical and neurological examinations conducted by Dubowitz et al.
Umbilical or peripheral venous blood was collected from all the subject infants within two hours after their birth, after which the blood was transferred into an EDTA-treated sample bottle. In the hospital, according to the evaluation guideline on infants with very low birth weights, peripheral venous blood was collected on the third day, seventh day, second week, and fourth week after birth, using the aforementioned method, after which the hemoglobin, hematocrit, WBC count, and platelet count were measured. The nRBC count was described per 100 WBC through the Wright stain of the blood smear, and was then converted into the absolute count over the corrected WBC count to calculate the absolute nRBC count. The corrected WBC count and the absolute nRBC count were calculated as follows
Student's t-test was conducted using the SPSS software (version 12.0, Chicago, IL, USA) for statistical analysis. The mean and continuous variables were expressed as mean±standard deviation. To determine whether the nRBC count has a correlation with birth weight and gestational age, one-way ANOVA was used for the comparison of the three groups. Receiver-operating characteristics (ROC) curve analysis was performed to evaluate the predictive accuracy of nRBC for severe IVH and death. It was considered statistically significant if the
This study was conducted on a total of 126 VLBWIs and who were hospitalized in the NICU. Of these infants, 14 infants with congenital anomalies, chromosomal abnormalities, twin-to-twin transfusion, expected death within 48 hours after birth, and severe anemia were excluded from the study. The study population consisted of 55 males (49.1%) and 57 females (50.9%). As for the delivery mode, 29 cases (25.9%) had spontaneous vaginal delivery, and 83 cases (74.1%) had Cesarean section. The mean birth weight was 1,135±229.83 g, and the mean gestational age was 204.87±17.76 days. The mean maternal age was 30.18±4.76 years, and the mean hospitalization duration was 63.64±26.87 days. The mean 1-min Apgar score was 3.75±1.75 points whereas the mean 5-min Apgar score was 5.58±1.75 points. 5-min Apgar scores of 6 points or less were shown in 75 cases (67.1%); SGA was shown in 19 cases (17%); HMD was shown in 76 cases (67.9%); BPD was shown in 38 cases (33.9%); grade 3 or higher ROP was shown in 17 cases (16%), of which 14 infants had grade 3 and three had grade 4; PDA was shown in 58 cases (51.8%); grade 3 or higher IVH was shown in six cases (5.4%), of which one infant had grade 3 and five had grade 4; necrotizing enterocolitis (NEC) was shown in eight cases (7.1%); pulmonary hemorrhage was shown in two cases (1.8%); and death was shown in 13 cases (11.6%) (
The mean nRBC and mean absolute nRBC counts in 112 VLBWIs were 33.93±43.34/100 WBC and 2.4±2.75×109/L, respectively, at birth; 19.86±27.72/100 WBC and 1.58±2.62×109/L, on the third day after birth; 8.12±22.45/100 WBC and 0.85±2.43×109/L, on the seventh day after birth; 4.7±7.99/100 WBC and 0.58±0.86×109/L, in the second week after birth; 4.49±5.35/100 WBC and 0.42±0.43×109/L, in the third week after birth; and 4.52±3.93/100 WBC and 0.4±0.36×109/L, in the fourth week after birth. These results showed that the nRBC and absolute nRBC counts gradually decreased with the passage of time after birth, and had constantly low values since one week after birth (
When the infants were classified into three groups based on their birth weights (less than 1,000 g, 1,000 g or more to less than 1,250 g, and 1,250 g or more), and were then compared, the nRBC counts at birth (
In determining the correlation of the nRBC count with the perinatal complications, when the 5-min Apgar score was 6 points or below, the mean nRBC count at birth was 44.4±51.7/100 WBC, which was significantly higher compared to the control group (
In addition, no significant difference in nRBC count was found in the cases of sex and delivery mode. The absolute nRBC count showed the same statistical significance as that of the nRBC count in the same group, except for a difference at birth in the case of death.
Among the factors that showed the correlation of the nRBC count with the perinatal complications in VLBWIs, multiple linear-regression analysis was conducted on death, neonatal asphyxia, IVH, NEC, HMD, BPD, pulmonary hemorrhage, birth weight, and SGA to identify the expected risk factors. Death showed a close correlation with the mean nRBC count at birth (coefficient: 35.7; 95% CI: 9.2-62.2), on the third day after birth (coefficient: 31.3; 95% CI: 14.1-48.5), on the seventh day after birth (coefficient: 30.0; 95% CI: 14.8-45.2), and on the 14th day after birth (coefficient: 12.2; 95% CI: 5.6-18.8) (
In the cutoff evaluation of grade 3 or higher IVH and perinatal death by ROC curve analysis, which showed a higher correlation with the nRBC count. The area under the ROC curve (AUC) was 0.919±0.046 on the nRBC count on the seventh day after birth with grade 3 or higher IVH. And it was 0.848±0.082 on the nRBC count on the third day after birth with perinatal death (
Excluding the 18 infants with perinatal death and grade 3 or higher IVH, where a higher correlation was shown among the factors that showed statistical significance in the multiple linear-regression analysis, the nRBC and absolute nRBC counts based on the birth weight and gestational age were reviewed in 94 infants to determine the reference count. The reference count of the nRBC count was 27.04±28.37/100 WBC at birth, 13.7±18.2/100 WBC on the third day after birth, and 3.1±3.0/100 WBC on the seventh day after birth, showing a continuous decrease after birth. No significant change in the mean nRBC count was found, however, since the seventh day after birth. When classified based on birth weight, the reference count of the nRBC count was 32.1±31.2/100 WBC in the case of those with a birth weight of less than 1,000 g, 25.2±23.1/100 WBC in the case of those with a birth weight of 1,000-1,249 g, and 27.0±28.4/100 WBC in the case of those with a birth weight of 1,250 g or more. When classified based on gestational age, the reference count of the nRBC count at birth was 25.1±29.4/100 WBC in the case of those with a gestational age of less than 28 weeks, 27.4±28.9/100 WBC in the case of those with a gestational age of 28-31 weeks, and 27.9±27.3/100 WBC in the case of those with a gestational age of 32 weeks or more. Since then, decrease in the nRBC count showed the same pattern (
Several studies have been reported on nRBC and absolute nRBC in full-term infants. However, no study has been conducted on VLBWIs, and on the reference count based on gestational age and birth weight as well as the normal count based on the stage after birth in premature infants. The mean nRBC and mean absolute nRBC counts at birth in a full-term infant's cord blood were 3.3±3.9/100 WBC
Previous studies have reported the correlation of neonatal asphyxia and nRBC count
Philip et al.
Although the nRBC count increased significantly in the infants with HMD in domestic studies
Ahmet et al.
The mean nRBC count increased significantly in the group with perinatal death at birth, on the third day, on the seventh day, and on the 14th day after birth compared to the control group. These results were consistent with those of the other studies that showed an increased mean nRBC count in the group with death
There are two ways of describing the nRBC count. One way is per 100 WBC, and the other by the absolute nRBC count, which is corrected based on the corrected WBC count. Under the condition where leukocytosis such as neonatal asphyxia or sepsis can occur due to the variation in the WBC count, the absolute nRBC count was reported to be more accurate
In the cutoff evaluation of perinatal death and grade 3 or higher IVH, which showed a higher correlation with nRBC count, when the cutoff value was set at 32.5/100 WBC on the third day after birth and at 12.5/100 WBC on the seventh day after birth based on the mean nRBC count of 19.9/100 WBC on the third day after birth and of 8.1/100 WBC on the seventh day after birth, the highest sensitivity and specificity over perinatal death and severe IVH were shown. These results could be useful in that they point out that specificity is more important than sensitivity when it comes to disease severity.
This study is a retrospective one with a few restrictions, such as the fact that nRBC counting could be on weekdays, so no evaluation of the nRBC count in a test was conducted on weekend, only evaluation of late sepsis as there are no infants diagnosed with early sepsis, no evaluation of various factors, such as the measurement of the fetus blood flow volume and cord blood, and evaluation of multivariate analysis was not conducted. The results of this study, however, present the nRBC count for reference purposes based on birth weight and gestational age in VLBWIs. They also show that the mean perinatal nRBC count in VLBWIs is inversely proportional to the birth weight and gestational age, and exhibit the highest peak at birth and continuous decrease after birth. If no decrease or increase in the nRBC count is observed, precautions on newborn infant care should be required as perinatal poor prognoses such as newborn infant death, severe IVH, and NEC could be associated. A further study on the correlation of the nRBC count with perinatal complications will be required.
Receiver operating characteristic (ROC) curves of nucleated red blood cell counts on 3rd and 7th days afterof birth and 7th day of birth in patients with grade III or higher intraventricular hemorrhage (A) and death (B). Area under ROC curves (95% confidence interval) were 0.624, 0.919 (A), and 0.848, 0.698 (B).
Clinical Characteristics of the Study Patients
Abbreviations: No, number of cases; SD, standard deviation
Mean nRBC Counts on Each Days
Data shown as mean ± SD
Abbreviations: nRBC, nucleated red blood cell; ANRBC, absolute nucleated red blood cell
Comparison of nRBC Counts Based on Birth Weight and Gestational Ages
Data shown as mean ± SD
*
Correlation of the nRBC Counts and Perinatal Complications
Data shown as mean±SD
*
†
‡IVH grade III and IV
Abbreviations: IVH, intraventricular hemorrhage; NEC, necrotizing enterocolitis
Multiple Linear Regression between nRBC Counts and Perinatal Complications
Abbreviations: HMD, hyaline membrane disease; BPD, broncho-pulmonary dysplasia; NEC, necrotizing enterocolitis; IVH, intraventricular hemorrhage; SGA, small for gestational age
Cut-off Values of nRBC Counts(/100WBCs) of Intraventricular Hemorrhage and Death
Abbreviations: IVH, Intraventricular hemorrhage; PPV, positive predictive value; NPV, negative predictive
nRBC Counts Reference Value of Based on Birth Weight and Gestational Ages
Data shown as mean ±SD
Abbreviation: nRBC, nucleated red blood cell
Absolute Nucleated Red Blood Cells Counts Reference Value of Based on Birth Weight and Gestational Ages
Data shown as mean ±SD
*
Abbreviation: nRBC, nucleated red blood cell