Reduction in hospital readmission rates for hyperbilirubinemia is associated with use of transcutaneous bilirubin measurements.

The use of transcutaneous bilirubin (TcB) measurements would seem to represent an opportunity to decrease the use of laboratory total serum bilirubin (TSB) testing because the former would serve as a surrogate for the latter. Many authors of previous studies have concluded that TcB measurements are useful and can serve as a reliable index for estimating TSB concentrations (1–4), even in darkly pigmented neonates (5 ). Although the use of TcB measurements might represent, correspondingly, an opportunity to decrease expenses by decreasing laboratory TSB measurements, such a consequence would be dependent on several factors, including the cost of personnel and reagents for performing the TcB measurements and the number of TcB measurements performed. In addition, the TcB results might impact other caretaker practice behaviors, such as the ordering of TSB measurements and compliance with guidelines for the application of phototherapy, whether used in or outside the hospital, as governed by local practice routines. The newly revised American Academy of Pediatrics (AAP) Clinical Practice Guideline on management of hyperbilirubinemia in the newborn (6 ) would not necessarily affect or predict the interaction of these factors. In this issue of Clinical Chemistry, Petersen et al. (7 ) demonstrate that the introduction of TcB measurements for the identification of infants with hyperbilirubinemia was followed by a decrease in the number of hospital readmissions of infants with hyperbilirubinemia per 1000 births/month. However, they found that the interaction of various factors did not contribute to changes in the length of stay for normal newborns and that new costs, in addition to those for TcB measurements, arose from an increased use of laboratory TSB testing and increases in the number and proportion of infants treated with phototherapy. Thus, the net effect of introducing TcB measurements was an increase in overall charges but, arguably, a safer manner of practice, leading to fewer readmissions for hyperbilirubinemia, most likely because of an increase in infants undergoing phototherapy. This retrospective study is challenged in the usual ways in that it reports only on the consequences of changes in caretaker behavior after the introduction of TcB testing as a diagnostic measurement option. Although decisions to start phototherapy or obtain additional TSB measurements were guided by the Bhutani nomogram (8 ), the actual decisions to measure TcB or TSB and, ultimately, to initiate phototherapy were made by the attending physician and were not dictated by a strict practice protocol. Perhaps if additional rules had been introduced to direct the use of routine TSB testing, then such testing might have been decreased, leading to a reduction in total overall costs. Use of the Bhutani nomogram is also recommended in the new AAP Guideline (6 ). This nomogram uses relatively low concentrations of bilirubin for assignment of risk for hyperbilirubinemia and in the evaluation of causation. These bilirubin concentrations are not thresholds at which treatment is recommended. Separate nomograms (6 ) are used for decisions to institute phototherapy and other therapies that are initiated at higher thresholds. Clinicians should not use the Bhutani nomogram for treatment decisions; such use would increase unnecessarily the application of phototherapy or other therapies. Nonetheless, it is not necessarily a “bad thing” for more infants to be treated for hyperbilirubinemia, if indeed they do qualify for such an intervention. This is especially so when treatment prevents future readmissions, an event that, in itself, implies that infants are exceeding hourspecific TSB concentrations that represent risks to their health. On the other hand, the argument can be made, justifiably, that adding TcB screening introduces no real advantage over TSB testing unless it replaces such invasive testing, particularly considering that the effort is undertaken to avoid rare injuring events among otherwise healthy near-term and term infants. If TcB screening could replace much of the TSB testing, then the introduction of a surrogate device could be better rationalized. Certainly, there are situations in which TSB testing is not readily available and TcB determinations would allow compliance within the AAP Guideline (5 ). The blanket statement that skin pigmentation has been found to have no effect on TcB measurement could lead to an inappropriate lack of attention to certain population differences that could impact the relationship between TcB and TSB. For example, the presence of light-absorbing, nonbilirubin, nutrition-derived yellow pigments in the skin of infants could affect this relationship (9 ). The consumption of carotene-containing red palm oil, fruits, and vegetables may be high in certain populations, such as the ones studied in Nigeria (5 ). Moreover, dietary fat-soluble carotenoids can be transferred through breast milk. In as much as the physical and optical characteristics of the carotenoids and bilirubin are similar, the correlation between TcB and TSB could be affected by carotenodermia, although this is unlikely to be a common problem in the United States. In addition, protecting the test site on the forehead from phototherapy is necessary with implementation of TcB testing and should not be overlooked. If measurements of TcB and TSB are compared regularly within a single institution, a reliable relationship between the two measurements can be documented. The manufacturer recommends validation of TcB twice a year, with TSB measured in serum specimens within 1 h. This may not always be possible. For this validation to be meaningful, it must be done in a sizeable number of specimens, and these may not always be available. If an infant were to have TcB readings performed at one institution and the TSB performed at another, any assumption about the relationship between TcB and TSB would be questionable because the variability of TSB Editorial