REVISED REFERENCE RANGES FOR CIRCULATING NEUTROPHILS IN VERY-LOW-BIRTH-WEIGHT NEONATES

Objective. Healthy very-low-birth-weight neonates (VLBW, less than or equal to 1500 g) exhibit a high incidence of neutropenia according to Manroe's reference ranges for neutrophil indices. Since these referenc e ranges may be inappropriate for VLBW neonates, we determined the ref erence ranges for circulating peripheral neutrophils in VLBW neonates between birth and 28 days of age. Methods. Serial, timed peripheral wh ite blood cell counts (n = 1788) were prospectively obtained between b irth and 28 days from 193 inborn, VLBW neonates delivered between Janu ary 1 and December 31, 1990. Data were divided into neutrophil counts obtained prior to (n = 630) and after (n = 1158) 60 hours of age. Afte r excluding counts from neonates with perinatal and/or neonatal compli cations, values from ''normal'' neonates were compared to Manroe's ref erence ranges. Where indicated new ranges were developed. Results. Alt hough immature neutophil (ATI) and immature:total neutrophil (I:T) val ues were within Manroe's reference ranges (P > .1) throughout the neon atal period, 67% of total neutrophil values (ATN) obtained prior to 60 hours of age were outside (P < .001) and 95% were considered neutrope nic. Newly developed ATN reference ranges for VLBW neonates have a wid er range of distribution compared to Manroe's results, primarily refle cting a decrease in the lower boundary. ATN values between 61 hours an d 28 days also differed (P < .001), and new ranges had upper and lower boundaries of 6000 and 1100/mm,(3) respectively. Maternal hypertensio n was associated with neonatal neutropenia (P < .001) without abnormal ities of ATI or I:T prior to day 3 of life; however, neutrophilia pred ominated after day 7. Between birth and 28 days <70% of ATN values wer e abnormal in neonates with apnea, neutrophilia occurring in >90% of c ounts; I:T values, however, were normal between 61 hours and 28 days. Conclusions. Normal preterm VLBW neonates have ATN reference ranges th at differ significantly from that for larger, older neonates, demonstr ating the effects of development on neutrophil dynamics. The predictab ility of neonatal infection using these new reference ranges requires additional study.