[Risk factors for neutropenia of late newborns]

To study the risk factors and treatment for neutropenia of late newborns (NLN).

Related clinical data were collected from the preterm infants and critically ill neonates who were admitted to the neonatal intensive care unit from July 2019 to January 2020. A total of 46 newborns with a blood absolute neutrophil count (ANC) of < 1.5×10⁹/L for two consecutive times at weeks 2-4 after birth were enrolled as the NLN group. A total of 92 late newborns with a blood ANC of ≥ 1.5×10⁹/L, matched at a ratio of 1:2, were enrolled as the control group. Possible risk factors associated with NLN and the treatment process were recorded. A logistic regression analysis was performed to identify the risk factors for NLN.

Among the 46 neonates in the NLN group, 29 had a gestational age of < 32 weeks, 14 had a gestational age of 32-37 weeks, and 3 had a gestational age of > 37 weeks. There was no significant difference between the two groups in the incidence rates of gestational hypertension, premature rupture of membranes > 18 hours and intrauterine distress, 5-minute Apgar score, the duration of positive pressure ventilation, the incidence rate of early-onset sepsis, and the type of initially used antibiotics (P > 0.05). Compared with the control group, the NLN group had a higher incidence rate of late-onset sepsis and a longer duration of antibiotic use (P < 0.05). Late-onset sepsis and prolonged duration of antibiotic use were independent risk factors for NLN (P < 0.05). With the presence of late-onset sepsis, the risk of NLN was increased by 1.537 times in neonates, and the risk of NLN was increased by 76.9% for every 3-day increase in the duration of antibiotic use. The mean age at the diagnosis of NLN was (21±6) days for the 46 neonates in the NLN group. Thirteen neonates with NLN were administered with recombinant human granulocyte colony-stimulating factor (G-CSF, 10 μg/kg) once or twice. O the 13 neonates, 6 had an ANC of < 0.5×10⁹/L and 7 had a gestational age of < 32 weeks or severe disease conditions. After treatment the ANC returned to > 1.0×10⁹/L in the 13 neonates. No drug-related adverse reactions were found. After the diagnosis of NLN, 2 neonates developed sepsis, and the remaining 44 neonates did not develop any common purulent infections.

The risk of NLN increases with the presence of late-onset sepsis and the increase in the duration of antibiotic use. NLN is generally a benign process. G-CSF appears to be safe and effective for NLN with severe disease conditions or severe reduction in ANC.