What is the principle of the transcutaneous bilirubin assay?

The transcutaneous bilirubin assay utilizes the principle of multiwavelength reflectance photometry. This method involves shining light of various wavelengths onto the skin, particularly in areas where bilirubin tends to accumulate, such as the forehead. The device then measures the light reflected back from the skin.

Bilirubin absorbs light at specific wavelengths; by using multiple wavelengths, the device can accurately assess the concentration of bilirubin in the skin's interstitial fluid. The technique is non-invasive and provides a quick estimation of bilirubin levels, making it particularly useful for screening hyperbilirubinemia, especially in newborns. The reflectance of light changes depending on the bilirubin concentration, allowing for a reliable measurement without the need for blood sampling.

Other methods mentioned, such as infrared absorption or laser fluorescence analysis, are not typically employed in transcutaneous bilirubin measurement. These approaches are more suited for other types of analysis in the clinical laboratory. Colorimetric change detection is a different technique used for direct measurements in sample solutions rather than being applicable to measuring bilirubin levels through skin reflectance.