Jaybose et al reported the RDW index (RDWI) as a method of distinguishing iron deficiency anemia from thalassemia trait. The authors are from New York Medical College in Valhalla.

Patient selection: mild microcytic anemia (hemoglobin >= 8.0 g/dL)



(1) MCV in femtoliters

(2) RBC in 10^12/L

(3) RDW in percent


RDW index =

= ((MCV) / (RBC)) * (RDW)



Hoffman et al uses (MCV) / ((RBC) * (RDW)) but this gives poor results.



A score > 220 is associated with iron deficiency anemia.

A score < 220 is associated with thalassemia trait.



The sensitivity was 91% and specificity 91% for diagnosis of iron deficiency anemia.

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