Physics and biology of transcutaneous bilirubin assay

Obtaining a transcutaneous bilirubin (TcB) measurement is a rather simple and straightforward process that is carried out thousands of times each day in hospitals and in other medical settings throughout the world. However, the physics and biology behind TcB measurements are actually rather complex. The purpose of this chapter is to briefly review the optical properties of human skin and subcutaneous tissue and to explain the biochemistry of bilirubin in the skin. An understanding of these topics is necessary in order to appreciate how transcutaneous bilirubinometry works and how it provides the clinical information that is used routinely.