What defines polycythemia in term neonates?

Polycythemia in term neonates is defined primarily by a hematocrit greater than 65%. This condition arises when there is an increased concentration of red blood cells in the bloodstream. In neonates, particularly those who are born at term, a hematocrit level exceeding 65% indicates a state of polycythemia, which can lead to increased blood viscosity and potential complications such as hyperbilirubinemia or respiratory distress.

While elevated hemoglobin levels and red blood cell counts can indicate polycythemia, the hematocrit is the most clinically relevant and widely accepted measure for defining this condition in neonates. Values such as hemoglobin above 14 g/dL and red blood cell counts over 6 million cells/uL may reflect increased cell mass, but they do not provide as definitive a threshold specific to diagnosing polycythemia as the hematocrit measurement does. Additionally, hyperbilirubinemia associated with jaundice is a potential consequence of polycythemia but does not serve as a diagnostic criterion for the condition itself. Thus, the hematocrit level remains the key parameter for defining polycythemia in this population.