Making Sense of Transferrin Tests

In his article, "Anemia: A Strategy for the Workup"(CONSULTANT, June 2002, page 869), Dr James Berginmakes several references to a test that measures the"serum transferrin receptor level." Is this the same testas that which is commonly referred to as a "transferrinlevel" test?
-- David Myers, BSMT
    Coordinator of Medical Laboratory Services
    St Louis County Department of Health, MoTransferrin usually refers to the plasma iron-bindingprotein that carries the iron in the circulatorysystem to cells. It is measured by the amount ofiron it will bind; namely, the plasma iron concentrationand the total iron-binding capacity.The serum transferrin receptor is the transmembraneprotein that facilitates the entry of transferrin-bound ironinto cells. It is measured using an enzyme-linked immunosorbentassay (ELISA) procedure and a monoclonal antibody.A number of companies offer this test.
-- James Bergin, MD
    Professor of Medicine, Emeritus
    University of Kansas Medical Center
    Kansas City