In red cell volume determination, why is ascorbic acid added to labeled RBC?

Ascorbic acid is used in the determination of red cell volume to prevent additional tagging. In the context of labeled red blood cells (RBC), it serves as a reducing agent that helps to prohibit further binding of labeling agents or tags to the RBCs after the initial tagging process has occurred. This is crucial to ensure that the measurements taken reflect the initial labeling without any interference from unbound labeling agents that could potentially alter the volume calculations.

By preventing subsequent tagging, ascorbic acid contributes to more accurate and consistent quantification of red cell mass, which is vital in various diagnostic assessments in nuclear medicine. The accuracy of these measurements is key in evaluating conditions such as blood loss or disorders affecting red cell mass.