Tcb Levels In Newborns: Understanding The Norms

Transcutaneous bilirubin (TcB) is a non-invasive procedure used to detect hyperbilirubinemia in newborns. It is a safe alternative to total serum bilirubin (TSB) measurement, which is the gold standard for diagnosing hyperbilirubinemia but is invasive and stressful for newborns. TcB devices are commonly used in hospitals to measure bilirubin levels in newborns before discharge, as early detection of hyperbilirubinemia is crucial to prevent severe hyperbilirubinemia, which can lead to encephalopathy and other serious health conditions.

TCB levels and hyperbilirubinemia

Hyperbilirubinemia is a common condition in newborns, with a prevalence of around 60% in full-term babies and 80% in premature babies. It is caused by a buildup of bilirubin in the blood when the liver is unable to get rid of it effectively. Bilirubin is a yellow substance produced when red blood cells break down, and it is normally removed from the body through bile.

Normal total serum bilirubin (TSB) levels in newborns can range anywhere between 1.0 and 12.0 mg/dL. However, TCB levels are typically measured using a transcutaneous bilirubinometer, a non-invasive device that measures bilirubin levels in the skin.

Using TCB Levels to Predict Hyperbilirubinemia:

A study conducted by Sampurna et al. (2020) aimed to determine whether TCB levels measured during the first day of life could be used to predict hyperbilirubinemia at 48 and 72 hours in preterm neonates. The study found that TCB values in the early days of life can be used as predictors of hyperbilirubinemia in subsequent days.

The study divided preterm neonates into two groups based on weight: Group I (1000-1500 grams) and Group II (1501-2000 grams). TCB levels were measured at 12, 24, and 72 hours of age. The following TCB cut-off values were determined to predict hyperbilirubinemia:

• For Group I, a TCB level of 4.5 mg/dL at 24 hours predicted hyperbilirubinemia at 48 hours.
• For Group II, a TCB level of 5.8 mg/dL at 24 hours predicted hyperbilirubinemia at 48 hours, and a TCB level of 5.15 mg/dL at 24 hours predicted hyperbilirubinemia at 72 hours.

Treatment of Hyperbilirubinemia:

Mild cases of hyperbilirubinemia typically resolve on their own as the baby's liver matures. Feeding the baby frequently can help encourage bowel movements, aiding in the excretion of bilirubin.

If bilirubin levels are high or continue to rise, phototherapy is the standard treatment. The baby is placed under special blue or white lights, which help break down bilirubin so that it can be excreted without being processed by the liver.

In rare cases, an exchange transfusion may be necessary, where some of the baby's blood is replaced with fresh, donated blood.

Complications of Hyperbilirubinemia:

Untreated severe hyperbilirubinemia can lead to serious health conditions such as cerebral palsy, deafness, and kernicterus (a type of brain damage). High levels of unconjugated bilirubin in newborns can cross the blood-brain barrier and harm their developing brains. Therefore, it is important to monitor bilirubin levels and provide treatment if necessary.

TCB levels and jaundice

Jaundice is a common condition in newborn babies, characterised by a yellowing of the skin and eyes. It is caused by a build-up of bilirubin in the blood, which occurs when the liver is not yet developed enough to get rid of it. Typically, jaundice is not serious and goes away on its own within a couple of weeks. However, it is important for a healthcare provider to check the baby for jaundice to ensure that bilirubin levels do not get too high, as this can lead to severe jaundice and, in rare cases, brain damage.

TCB Levels

The transcutaneous bilirubin (TcB) level is a measure of the amount of bilirubin in a newborn baby's blood. It is estimated by placing a probe on the baby's head. If the TcB level is high, a blood test will be ordered to confirm the results. This involves pricking the baby's heel to collect a small blood sample, which will show the total serum bilirubin (TSB) level.

Jaundice usually occurs within the first few days of a baby's life, when bilirubin levels are at their highest. During this time, it is important for a healthcare provider to monitor the baby's bilirubin levels. If levels are high or continue to rise, the baby may require treatment with phototherapy. This involves placing the baby under special blue lights to help their liver get rid of excess bilirubin.

In rare cases, if phototherapy is not effective, an exchange transfusion may be necessary. This involves replacing some of the baby's blood with fresh, donated blood.

To prevent severe jaundice, it is recommended to feed newborns frequently. This stimulates regular bowel movements, which help to rid the body of excess bilirubin.

TCB levels and phototherapy

Overview

Transcutaneous bilirubin (TCB) measurement is a non-invasive procedure used to identify hyperbilirubinemia in newborn infants. It is a safe and effective alternative to total serum bilirubin (TSB) measurement, which requires blood sampling and can be invasive and painful for the infant. TCB measurement can also reduce the need for blood sampling.

TCB Measurement Techniques

TCB is measured using a transcutaneous bilirubinometer, which estimates bilirubin levels by measuring the spectral reflectance of the infant's skin and subcutaneous tissue. The most common sites for TCB measurement are the forehead and the sternum, although other sites such as the back, hipbone, and interscapular space have also been used.

TCB and Phototherapy

Phototherapy is a common treatment for neonatal hyperbilirubinemia, which involves exposing the infant's skin to special blue lights. Phototherapy converts bilirubin into a more water-soluble form that can be excreted by the body. This process can affect TCB measurements, as the bilirubin in the skin is modified during phototherapy.

Impact of Phototherapy on TCB Measurements

Several studies have investigated the impact of phototherapy on the accuracy of TCB measurements. Some studies have found that TCB measurements during phototherapy tend to underestimate TSB, especially when bilirubin levels are high. However, other studies have reported insignificant differences between TCB and TSB measurements during phototherapy.

Optimal Timing and Location for TCB Measurements

The optimal timing and location for TCB measurements during phototherapy have been the subject of several studies. One study found that the forehead at 30 minutes after the cessation of phototherapy was the best time point and location for TCB measurement, as it showed the strongest correlation with TSB levels. Another study found that TCB measurements from a shielded area of the skin on the forehead during phototherapy correlated well with TSB measurements.

Recommendations for TCB Measurement During Phototherapy

Based on the available evidence, TCB measurements can be used to monitor bilirubin levels during phototherapy, but they should not be considered a surrogate for TSB measurements. It is recommended to perform TCB measurements at specific intervals during phototherapy and to confirm TCB results with TSB measurements, especially if the infant is found to have significant hyperbilirubinemia. Close monitoring is important for infants with TCB values higher than the established cut-off values.

TCB levels and preterm neonates

Transcutaneous bilirubin (TCB) is a non-invasive procedure used to identify hyperbilirubinemia in newborns. Hyperbilirubinemia is a common condition in newborns, with a prevalence of around 60% in term neonates and 80% in preterm neonates. Preterm neonates are at a greater risk of severe hyperbilirubinemia, which can lead to encephalopathy if not treated promptly.

TCB as a Predictor of Hyperbilirubinemia

A study conducted in Indonesia aimed to determine TCB cut-off values during the first day for preterm neonates to predict hyperbilirubinemia at 48 and 72 hours. The study found that TCB values in the early days of life can be used as hyperbilirubinemia predictors for the following days for preterm neonates.

The study included 90 preterm neonates born at ≤35 weeks, divided into two groups based on weight: Group I (1000-1500 grams) and Group II (1501-2000 grams). TCB levels were measured on the sternum at 12, 24, and 72 hours, and total serum bilirubin (TSB) measurements were taken on the third day or if the TCB level reached the phototherapy threshold.

The results showed that almost half of the neonates in Group I (45%) and Group II (46%) suffered from hyperbilirubinemia at 48 hours and 72 hours, respectively. The TCB cut-off values at 24 hours that best predicted hyperbilirubinemia at 48 hours were 4.5 mg/dL for Group I and 5.8 mg/dL for Group II. For Group II, the TCB cut-off value at 24 hours that best predicted hyperbilirubinemia at 72 hours was 5.15 mg/dL.

Visual Assessment vs. TCB

Visual assessment of jaundice is not reliable, especially in the first 24-48 hours after birth. Only 80% of jaundiced babies can be visually identified if the bilirubin level reaches >6 mg/dL. In contrast, TCB is a more reliable method for detecting hyperbilirubinemia, and it can reduce the need for blood sampling by 41-73%.

TCB in Clinical Practice

The American Academy of Pediatrics recommends routine checks of TSB or TCB, along with risk factor assessments in the first days of life. Daily TCB measurement is crucial for the early identification of hyperbilirubinemia, especially in preterm neonates, to prevent complications. Close monitoring should be arranged for those with TCB values higher than the cut-off values.

TCB levels and breastfeeding

Transcutaneous bilirubin (TCB) is a non-invasive procedure used to identify hyperbilirubinemia in newborn infants. It is a safe alternative to total serum bilirubin (TSB) measurement, which is the gold standard for diagnosing hyperbilirubinemia but is an invasive procedure that can be stressful for the newborn. TCB is a useful tool for early detection and prediction of hyperbilirubinemia, which is common in newborn infants and, in severe cases, can lead to encephalopathy and even death.

Breastfeeding is important for infant health and development and has many benefits, but breastfed infants are at a higher risk of developing hyperbilirubinemia than formula-fed infants. This is because breastfeeding jaundice can occur when a baby does not get enough breast milk, and also because substances in breast milk can affect how an infant's liver breaks down bilirubin, leading to a buildup.

To prevent hyperbilirubinemia, it is recommended that exclusively breastfed infants are fed eight to 12 times per day during their first week of life. This is because frequent feeding stimulates regular bowel movements, which help the baby get rid of excess bilirubin.

TCB measurement is a useful tool for monitoring bilirubin levels in breastfed infants, as it is non-invasive and can be used to predict the chances of developing severe hyperbilirubinemia. By plotting TCB measurements on a nomogram according to the infant's age in hours, it is possible to identify infants at low, intermediate, or high risk of developing severe hyperbilirubinemia and guide the timing of post-discharge follow-up evaluations.

If an infant is identified as being at high risk of developing severe hyperbilirubinemia, they may require phototherapy or, in severe cases, an exchange transfusion to lower their bilirubin levels.

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