Neonatal Transcutaneous Bilirubin Measurements: An Opportunity to Enhance Laboratory Utilization and Improve Patient Care

Abstract

By far the most common clinical problem addressed by family practitioners and pediatricians in the first weeks of an infant's life is hyperbilirubinemia. With the exception of the standard metabolic screen, the measurement of a total serum bilirubin (TSB)2 concentration is the most common laboratory test ordered for a newborn infant. That is not surprising because the clinical sign, jaundice, is seen in approximately 80% of infants in a well-baby nursery during the first few days (1). The process of observation, clinical monitoring, and laboratory testing that continues throughout the infant's first week of life has a single objective—to prevent extreme hyperbilirubinemia [a TSB concentration >25–30 mg/dL (>428–513 μmol/L)] and its rare but dreaded consequence, bilirubin encephalopathy. Data from most of the Western world suggest that chronic bilirubin encephalopathy, or kernicterus, is currently occurring at an incidence of approximately 0.5–2 per 100 000 live births (2). Thus, of approximately 4 × 106 infants born annually in the US, perhaps 20–40 will develop kernicterus, a permanently disabling condition characterized by athetoid cerebral palsy, severe sensorineural hearing loss, paralysis of upward gaze, and dental dysplasia. For decades practitioners have relied on the appearance and intensity of jaundice as a means of deciding when to obtain a TSB measurement, but recognizing that estimating TSB by eye is difficult and on occasion grossly misleading (3) has prompted the development of transcutaneous bilirubinometry. The instruments that measure the transcutaneous bilirubin (TcB) concentration operate by transmitting light that penetrates the blanched skin and transilluminates the subcutaneous tissues. The …