What is the primary characteristic of EDTA?

EDTA, or ethylenediaminetetraacetic acid, functions primarily as a calcium-binding agent. This characteristic makes it particularly valuable in the field of laboratory medicine and phlebotomy because it effectively prevents clotting in collected blood samples. When EDTA is present in blood tubes, it binds free calcium ions, which are necessary for the coagulation process. This binding leads to anticoagulation, allowing for the accurate analysis of blood components, particularly when performing complete blood counts or other tests that require whole blood to remain in a liquid state.

In the context of this question, while EDTA does act as an iron chelator and may have some implications on glucose metabolism, its primary role in blood collection tubes is to inhibit clot formation by binding calcium. This feature is crucial for ensuring that laboratory test results reflect the true composition of blood without the interference of clotting factors.