Diagnosing Anemia in Neonates: An Evidence-Based Approach

It is important for clinicians who render neonatal care to precisely and reproducibly diagnose anemia; however, confusion arises from various definitions. For the simplicity and consistency of detection, we advocate defining neonatal anemia as a hemoglobin level or hematocrit below the 5th percentile of the reference population, which is highly dependent on gestational and postnatal ages. Thus, a newborn infant delivered at 24 weeks' gestation will have anemia with a blood hemoglobin concentration much lower than a hemoglobin concentration defining anemia at term. Moreover, a hemoglobin concentration defining anemia at term birth is higher than that defining anemia in the same infant 60 days after birth. Diagnosing neonatal anemia can be evidence-based and consistent by using reference intervals derived from large neonatal databases. To do this, we advocate defining anemia as a hemoglobin level that plots below the 5th percentile lower reference interval, defining moderately severe anemia as a hemoglobin value between the 1st and 5th percentile, and defining severe anemia as a hemoglobin level that plots below the 1st percentile. The information provided in this review can easily be adopted by clinical laboratories and individual neonatal care units, thereby fostering application of these definitions for all infants whose hemoglobin levels are measured. Additional normative values included in this review describing various other erythrocyte metrics can likewise be easily adopted. Doing so will codify and standardize the diagnosis of neonatal anemia and will facilitate identifying the cause of the anemia, thus pointing the way to proper additional diagnostic testing and treatment.