BEYOND THE UMBILICAL-CORD - INTERPRETING LABORATORY TESTS IN THE NEONATE

Interpretation of biochemical testing in the neonatal period is challe nging because of the complexity of perinatal physiology, the difficult y of establishing appropriate laboratory reference ranges, and the tec hnical aspects of analyzing microvolume specimens that are often hemol yzed, lipemic, or have a high hematocrit or bilirubin concentration. M etabolic problems such as hyperbilirubinemia and hypoglycemia in the f ull-term neonate occur as the infant adapts from an intrauterine metab olism to extrauterine life. Pathophysiological processes in the premat ure infant vary with the severity of prematurity and the immaturity of metabolic systems. Interpreting neonatal biochemistry requires age- a nd gestation-specific reference ranges but technical, ethical, and phi losophical concerns continue to impair the development of the needed r eference data.