Neonatal transcutaneous bilirubin measurements: an opportunity to enhance laboratory utilization and improve patient care.

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) 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 mol/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 10 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 scattered light returns through a fiber optic filament, and the yellowness of the reflected light— corrected for the contribution of hemoglobin, melanin, and dermal thickness—is measured in a spectrophotometric module and converted into an estimate of the TSB concentration (3 ). Transcutaneous bilirubinometers measure the yellowness of the skin and subcutaneous tissues, and the contribution of the serum bilirubin to this measurement is minimal (4 ). Thus, a TcB measurement is not the equivalent of measuring TSB. Nevertheless, TcB and TSB measurements are highly correlated, and there are substantial data to confirm that TcB assessment, when used as a screening measurement, provides noninvasive, instantaneous, and clinically relevant information about the infant’s TSB concentration that cannot be obtained in any other way. Although many studies have evaluated the use of TcB in the immediate postdelivery hospital stay, the data are limited regarding the use of this technique at the doctor’s office or in the home. In a recent report, Wainer et al. (5 ) made an important contribution to our understanding of how TcB measurements can improve the care of newborn infants. These investigators studied 14 796 newborn infants 35 weeks of gestation and who were discharged from 3 newborn nurseries in Calgary, Canada. They assessed the impact of universal TcB screening combined with routine follow-up in the home or community clinic, and they compared the outcomes in this population with a historical cohort of 14 112 infants who had their bilirubin assessed by visual inspection alone. Wainer et al. used an existing public health nurse program that ensures that every infant born at one of the Calgary Health Region nurseries is seen within 1 to 2 days of discharge. The public health nurses, trained in newborn assessment and armed with a TcB device, obtained TcB measurements at the follow-up visit for all infants. Using a nomogram developed in their nurseries, the visiting public health nurse was able to decide whether a TSB measurement was necessary, whether the TcB assessment should be repeated within 24 h, or whether subsequent routine care was appropriate. Compared with the previous experience with visual inspection alone, the implementation of routine TcB measurements produced a 55% reduction (odds ratio, 2.219; 95% CI, 1.543–3.193; P 0.0001) in the incidence of TSB values 20 mg/dL ( 342 mol/L). 1 Department of Pediatrics, Oakland University William Beaumont School of Medicine, Division of Neonatology, Beaumont Children’s Hospital, Royal Oak, MI. * Address correspondence to the author at: Department of Pediatrics, Oakland University William Beaumont School of Medicine, Division of Neonatology, Beaumont Children’s Hospital, 3601 W. 13 Mile Rd., Royal Oak, MI 48073. Fax 248-551-5998; e-mail [email protected]. Received April 3, 2012; accepted April 24, 2012. Previously published online at DOI: 10.1373/clinchem.2012.183616 2 Nonstandard abbreviations: TSB, total serum bilirubin; TcB, transcutaneous bilirubin. Clinical Chemistry 58:10 000 – 000 (2012) Perspectives