To the Editor: The levels of ferritin and folate in the blood are regarded as the “gold standards” for measuring deficiencies in iron and folate, but they are complex and expensive tests. The red cell distribution width (RDW-CV%) measures variability in red blood cell (RBC) size, helps in early detection of deficiencies and is available in all automated analyses of RBCs. It is seldom listed on haematology reports, though it can be printed out at no extra cost. A raised RDW-CV% should prompt the treating doctor to consider underlying latent deficiencies and to order specific tests.
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