Point-of-Care Testing (POCT) bilirubinometry is a method for rapidly measuring bilirubin levels in newborns at or near the patient’s side. This technology is a screening tool to detect neonatal jaundice, a common condition in infants. The primary advantage of POCT is providing immediate results, allowing for prompt clinical decisions, which is especially useful with early hospital discharges. This quick assessment helps identify infants who may require further testing or treatment for high bilirubin levels.
The Science of Bilirubin and Jaundice
Bilirubin is a yellow pigment produced from the natural breakdown of red blood cells. Newborns produce more bilirubin than adults due to a higher rate of red blood cell destruction. An immature liver struggles to process this bilirubin, causing it to accumulate in the blood and deposit in the skin. This results in the yellowing of the skin and eyes known as jaundice, affecting about 60% of term and 80% of preterm infants in their first week.
While neonatal jaundice is often a temporary condition, extremely high levels of bilirubin can be toxic to the developing brain. If bilirubin concentration exceeds the binding capacity of albumin, a transport protein, it can cross the blood-brain barrier. This may lead to kernicterus, a rare but serious condition causing permanent neurological damage, including cerebral palsy, hearing loss, and death.
Because of these risks, timely screening for high bilirubin levels in all newborns is standard practice. Early detection allows for effective treatments, such as phototherapy, to prevent bilirubin levels from reaching a dangerous threshold. The goal is to identify at-risk infants and intervene before neurological damage can occur.
How POCT Bilirubinometry Works
POCT bilirubinometry uses two main types of devices. The first is the transcutaneous bilirubinometer (TcB), a non-invasive device pressed against an infant’s skin, often on the forehead or sternum. It directs a flash of light into the tissue and analyzes the reflection to estimate bilirubin concentration, eliminating the pain of a blood draw.
The second type is a point-of-care blood analyzer. This minimally invasive device requires a small blood sample from a heel prick, which is applied to a test strip or cartridge. The strip is inserted into a portable reader that provides a quantitative measurement of total bilirubin within minutes. Some advanced analyzers used in neonatal intensive care units (NICUs) can also measure bilirubin along with other analytes from a single sample.
Clinical Use and Interpretation
POCT bilirubinometry is widely used for universal jaundice screening before newborns are discharged from the hospital. The American Academy of Pediatrics recommends this screening for all newborns at 24 to 48 hours of life. A TcB device is the common initial screening tool because it is non-invasive.
TcB screening results are interpreted based on the infant’s age in hours and risk factors for severe hyperbilirubinemia. Risk factors include a gestational age under 38 weeks, a family history of jaundice, or exclusive breastfeeding with poor intake. Clinicians use hour-specific charts to plot the bilirubin level and determine the infant’s risk.
If a TcB reading exceeds a predetermined threshold, or is close to the phototherapy treatment level, a confirmatory blood test for total serum bilirubin (TSB) is performed. The TSB test results then guide further management. This may include initiating phototherapy, a treatment that uses blue light to help break down bilirubin in the skin.
Accuracy and Limitations
While effective for screening, POCT devices have limitations. Transcutaneous bilirubinometers are less accurate than laboratory total serum bilirubin (TSB) measurements, which are the gold standard. TcB devices can underestimate TSB levels, especially at higher concentrations, which is why high readings require confirmation with a blood test.
Several factors influence TcB accuracy, including the infant’s gestational age, birth weight, and skin pigmentation. In infants with darker skin, melanin can interfere with light absorption, potentially leading to an underestimation of the bilirubin level. Additionally, TcB measurements are not reliable in infants currently undergoing or who have recently received phototherapy, as this results in a reading that is not reflective of the actual serum bilirubin level.
Despite these limitations, the correlation between TcB and TSB is good for screening term and late preterm infants. Its value is in safely ruling out significant jaundice, reducing the need for invasive blood draws. While point-of-care blood analyzers are more accurate than TcB, their performance can still vary compared to high-precision laboratory methods.