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Bilirubin testing is essential for diagnosing and managing liver diseases and neonatal jaundice. While traditional TSB measurement remains the gold standard, noninvasive TcB devices and handheld POC devices offer convenient alternatives with varying degrees of accuracy. Recent innovations in bilirubin sensors promise to further simplify and expedite bilirubin measurement, potentially transforming clinical practice.
Bilirubin is a yellow compound that occurs in the normal catabolic pathway that breaks down heme in red blood cells. Its measurement is crucial for diagnosing and managing various medical conditions, particularly liver diseases and neonatal jaundice. This article provides an overview of the different methods for measuring bilirubin levels, their accuracy, and their clinical applications.
Traditional Bilirubin Measurement
The gold standard for measuring bilirubin levels is through a blood sample processed in a laboratory. This method, known as total serum bilirubin (TSB) measurement, is highly accurate but requires invasive blood draws and laboratory processing, which can delay results and treatment decisions1.
Noninvasive Transcutaneous Bilirubinometry
Transcutaneous bilirubin (TcB) measurement devices offer a noninvasive alternative to TSB. These devices estimate bilirubin levels by measuring the yellow color of the skin. Studies have shown that TcB devices have high sensitivity (74% to 100%) for detecting hyperbilirubinemia, making them reliable for initial screening. However, their specificity ranges from 18% to 89%, indicating that positive results often need confirmation through TSB measurement1.
Point-of-Care Bilirubin Testing
Handheld point-of-care (POC) devices are emerging as a convenient option for bilirubin measurement. These portable devices can provide results within 30 minutes, making them suitable for rapid decision-making. A systematic review found that POC devices like Bilistick and BiliSpec are faster and require less blood volume compared to traditional laboratory-based methods. However, they also showed a mean difference in bilirubin levels, suggesting that their precision needs improvement for accurate neonatal jaundice management3.
Innovative Bilirubin Sensors
Recent advancements have led to the development of novel bilirubin sensors. For instance, a paper-based potentiometric sensor can selectively measure free bilirubin in serum, offering a disposable and easy-to-use option for point-of-care applications. This sensor requires only a small sample and provides results in less than two minutes, covering the clinically relevant concentration range of bilirubin in serum2.
Another innovative approach involves a ratiometric bioluminescent indicator (BABI) that changes color based on unconjugated bilirubin (UCBR) concentration. This method allows for highly sensitive and quantitative detection using a smartphone camera, making it a simple and rapid diagnostic tool5.