Can We Use a Transcutaneous Bilirubin Reading After Phototherapy?

Patient Presentation
A 4-day-old male came to clinic for his first examination after discharge from the newborn nursery. He was a full-term infant, born by normal spontaneous vaginal delivery to a G1P1 26 year old Asian mother who had a birth weight of 2958 grams. His hospital course had been complicated by a cephalohematoma of the left side of his head and hyperbilirubinemia that was close to meeting criteria for phototherapy at approximately 36 hours of life at 13.3 mg/dL (cut off 13.6 mg/dL). The team decided to treat him with phototherapy which he received for approximately 18 hours. At that time his serum bilirubin level was 10.6 mg/dL and then had rebounded to a level 6 hours later was 11.1 mg/dl. He was discharged home at approximately 60 hours of life with a weight that was 2825 grams (decreased 4.5%). He was breastfeeding every 2 hours with 4 wet diapers and several stool diapers that were transitioning. The past medical history showed that there was no ABO incompatibility, Coombs test was negative and he did not have sepsis symptoms. The family history was positive for cousins who had had hyperbilirubinemia as infants. The review of systems was negative.

The pertinent physical exam showed an alert male with weight of 2781 grams that was down 6% from birth weight. He examination was negative except for continued jaundice of his skin and eyes. The diagnosis of a well-appearing newborn with jaundice was made. A serum bilirubin level was obtained and was 13 mg/dL. He was sent home with follow up in 2 days. When staffing, the resident asked if a transcutaneous bilirubin could be used to evaluate the infant at this time after phototherapy. The attending remarked that there might be data about this question, but that he was unaware of an actual answer to it.

Unconjugated hyperbilirubinemia in the newborn is a normal occurence. After birth the infant must rely on its own relatively immature liver to detoxify metabolites, the infant’s gastrointestinal tract also is not yet working as well for excretion, the infant is usually slightly fluid deficient before breastfeeding and/or bottle feeding are well established, and there is increased breakdown of red blood cells as the fetus has a higher hemoglobin than an infant and thus an infant is relatively hemoconcentrated. The total bilirubin rises from 1.5 mg/dL to 6.5 mg/dL (+ or -2.5 mg/dL) over the first 3-4 days of life. A differential diagnosis of neonatal unconjugated hyperbilirubinemia can be found here. A differential diagnosis of conjugated hyperbilirubinemia can be found here.

Phototherapy uses the skin to change the bilirubin to the more water-soluble lumirubin by using blue light at wavelengths of 420-480 nm. In doing so it causes blanching of the skin which obviously will change TcB levels. Factors which influence correlation between transcutaneous bilirubin (TcB) and total serum bilirubin (TsB) include skin color, TcB measurement body location, TsB level, the specific make and model of TcB bilirubinometer and if phototherapy has been used. Most professional guidelines currently advise against using TcB for determining hyperbilirubin level after phototherapy because of limited data that is available to determine the accuracy and clinical validity after phototherapy. However use of transcutaneous bilimeters in both inpatient and outpatient settings is more common today than in the past and questions about their appropriate use should be asked as clinical practices evolve.

Learning Point
Below are some recent studies that have tried to evaluate different aspects of how long after phototherapy could TcB be used to appropriately evaluate an infant for hyperbilirubinemia.

  • Tan and Dong in 2003 evaluated 70 neonates during and after phototherapy. They found that TcB and TsB were correlated at ~18-24 hours after phototherapy cessation.
  • Fonseca in 2012 evaluated 39 infants during and after phototherapy and attempted to correlate TcB performed in covered and uncovered skin areas with TsB. Overall, they found that TcB tested in skin-covered areas correlated with TsB but TcB in skin-exposed areas did not.
    They were only able to follow patients 6 hours after phototherapy cessation. Therefore they were not able to determine when recovery of skin color occurred as it had not occurred by end of the 6 hours.

  • Grabenhenrich in 2014 evaluated 86 term and preterm infants during and after phototherapy to determine the difference in TcB to TsB at different time periods during and after phototherapy. They calculated safety margins and found that “In the first 8 hours after treatment, TcB levels of -7.3 mg/dL below the individual phototherapy threshold allowed safe rejection of confirmatory blood sampling. After 8 hours, that safety margin was reduced to approximately -5.0 mg/dL.”
  • Juster-Reicher in 2015 in a study similar to Tan and Dong, evaluated 371 term infants and followed paired TcB and TsB measurements up to 9 days of life. They found that TcB and TsB measurements correlated 8 hours after cessation of phototherapy.

Questions for Further Discussion
1. How do you use TcB in your clinical practices and when do you correlate with a TsB?
2. What helps you determine when and if a patient may need phototherapy or other treatment for neonatal jaundice?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Jaundice and Common Infant and Newborn Problems.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Tan KL, Dong F. Transcutaneous bilirubinometry during and after phototherapy. Acta Paediatr. 2003;92(3):327-31.

American Academy of Pediatrics Subcommittee on Hyperbilirubinemia. Management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. Pediatrics. 2004 Jul;114(1):297-316.

Fonseca R, Kyralessa R, Malloy M, Richardson J, Jain SK.
Covered skin transcutaneous bilirubin estimation is comparable with serum bilirubin during and after phototherapy.
J Perinatol. 2012 Feb;32(2):129-31.

Grabenhenrich J, Grabenhenrich L, Buhrer C, Berns M.
Transcutaneous bilirubin after phototherapy in term and preterm infants. Pediatrics. 2014 Nov;134(5):e1324-9.

Juster-Reicher A, Flidel-Rimon O, Rozin I, Shinwell ES. Correlation of transcutaneous bilirubinometry (TcB) and total serum bilirubin (TsB) levels after phototherapy. J Matern Fetal Neonatal Med. 2014 Sep 30:1-3.

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital