Hyperbilirubinemia is a term used to describe excess bilirubin levels in the blood. In newborns, this condition is called Neonatal hyperbilirubinemia and causes clinical symptoms in yellow color on the baby's skin or eye sclera. Neonatal hyperbilirubinemia, or also called Neonatal jaundice, is defined as a total serum bilirubin level above 5 mg per dL (86 μmol per L). 

Transcutaneous Bilirubin Measurement in Newborn
Newborn with icteric
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Neonatal hyperbilirubinemia is generally not dangerous, and no need for treatment in most cases. However, there is a conditioning serum bilirubin level in some infants that may rise excessively (> 25 mg / dL).  It needs concern because unconjugated bilirubin is neurotoxic. That causes lifelong neurologic sequelae (such as encephalopathy) in newborns. This dangerous condition is called kernicterus. 

Measuring Bilirubin Levels

The gold standard for hyperbilirubinemia is by directly measuring serum bilirubin levels. Weaknesses of this method are the risk of local infection and pain at the injection site; the examination results require a long time so that it has the potential to delay therapy decisions. Also, in areas where laboratories are not available, this examination can be difficult to carry out. This method causes pain and, if done repeatedly, can potentially cause anemia. 

a. Visual Bilirubin Measurement

Kramer first introduced the visual inspection of bilirubin as a clinical clue to the presence of yellow in newborns. Cephalocaudal progression, with five specific dermis zones:
  1. Head-neck
  2. The abdominal area around the umbilical
  3. Arms and legs
  4. Soles  (plantar) of the feet
The examination is carried out in a well-lit place by pressing on the baby's skin for a few seconds so that a yellow or no shadow appears on the skin and subcutaneous tissue.

b. Transcutaneous Bilirubin Measurement

Transcutaneous bilirubin (TcB) Measurement is an alternative to noninvasive bilirubin measurement.  These meters work by directing light into the neonate's skin and measuring the specific wavelength intensity returned. The wavelengths used are variable in different transcutaneous bilirubin meter. The meter analyzes the spectrum of optical signals reflected from the neonate's subcutaneous tissues. These optical signals are converted to an electrical signal by a photocell. These are analyzed by a microprocessor to generate a serum bilirubin value.

This examination is performed using a tool affixed to the baby's skin's surface in the forehead or sternum area and does not cause pain. This tool will shoot light into the baby's skin's surface and then assess the intensity of the wavelengths reflected by the skin and captured by the tool.

Transcutaneous bilirubin measurement is more accurate than the visual assessment for screening neonatal hyperbilirubinemia. It can assist in diagnosis in infants aged> 24 hours and gestational age> 35 weeks.

Recommendations Regarding the Use of Transcutaneous Bilirubin

The American Academy of Pediatrics recommends using serum or transcutaneous bilirubin tests in jaundiced infants 24 hours after birth. However, this clinical guideline also states that transcutaneous bilirubin testing still requires further research on the validation of the results, factors that influence the examination results, and the cost-effectiveness of this examination.

The Canadian Pediatric Society clinical guidelines state that screening for hyperbilirubinemia can use the transcutaneous bilirubin measurement method. However, this recommendation is weak and only has a grade C.

On the other hand, these clinical guidelines state that transcutaneous bilirubin measurement inaccuracy results in infants who have undergone phototherapy and skin color and thickness factors that can affect the results. Also, the accuracy level between devices varies, so that it is necessary to first test the tool's validation before applying this tool for screening.

The latest recommendations from the National Institute for Health and Clinical Excellence (NICE), last updated in 2016, suggest the use of transcutaneous bilirubin testing in infants> 35 weeks' gestation and postnatal age> 24 hours. However, if the results of transcutaneous bilirubin> 14.6 mg / dL, reconfirm by checking serum bilirubin. Serum bilirubin examination also needs to be done on infants aged <24 hours or born with gestational age <35 weeks.

The NICE clinical guideline also recommends further examination of the tool's cost-effectiveness and comparing accuracy between the available transcutaneous bilirubin meter devices. 

Effectiveness of Transcutaneous Bilirubin measurement

Mir SE et al. conducted a literature review. They found a 55% reduction in severe hyperbilirubinemia levels when using transcutaneous bilirubinometry as a screening tool compared with visual bilirubin examination using the Kramer method.

In this literature review, they found that implementing transcutaneous bilirubin screening in infants assessed jaundice based on visual inspection results would reduce the number of babies who needed to undergo serum bilirubin measurement by 79%. This indicates the potential use of transcutaneous bilirubinometry as a screening device for hyperbilirubinemia measurement. However, this research method has a limitation, the underdiagnosis risk in infants with hyperbilirubinemia, but it is not seen in the visual inspection results.

Effectiveness of Transcutaneous Bilirubin measurement in Premature Babies

Based on the last updated NICE guidelines in 2016, no recommendation for transcutaneous bilirubin measurement in preterm infants under 35 weeks' gestation. Nevertheless, a meta-analysis study by Shabuj MH et al., which included 28 studies with a total of 1910 patients, found that the results of transcutaneous bilirubin measurement had a correlation level close to the results of serum bilirubin measurement. This meta-analysis also suggests the location of transcutaneous bilirubin checking on the patient's forehead and sternum. 

Visual inspection of bilirubin by Kramer's method is the simplest and no-cost examination but has inaccurate results. Therefore, transcutaneous bilirubin measurement can be an alternative noninvasive examination method in newborns that is quite accurate. However, the use of this measurement method in preterm infants is still controversial and requires further research.

Transcutaneous bilirubin measurement has obstacles to be applied because of the availability and high price. However, the cost of the transcutaneous bilirubin is much cheaper than examining serum bilirubin.

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