What does δ-bilirubin refer to?

δ-bilirubin refers to bilirubin that is tightly bound to albumin. This form of bilirubin is considered less soluble in water and is typically found in the bloodstream. Its binding to albumin is crucial for transport, as it helps maintain bilirubin in a soluble form for transportation to the liver, where it can undergo further processing.

Understanding the context of δ-bilirubin is important in clinical chemistry. Unconjugated bilirubin, while it also plays a role in hepatic function, is not water-soluble and primarily exists in the free form, thus confusing its association with the albumin-bound state. Direct-reacting bilirubin, on the other hand, primarily refers to conjugated bilirubin that is soluble and can be detected more readily in laboratory tests such as the Van den Berg reaction.

Therefore, the term δ-bilirubin specifically highlights the bilirubin that is bound to albumin, which is a crucial aspect in evaluating bilirubin metabolism and hepatic function.