Red cell distribution width, free erythrocyte protoporphyrin, and England-Fraser index in the differential diagnosis of microcytosis due to iron deficiency or beta-thalassemia trait. A study of 200 cases of microcytic anemia.

Microcytic anemias are often encountered in clinical practice. In most cases they are due to iron deficiency, but in some geographical areas other diagnoses, such as that of beta-thalassemia trait, must be considered. In some cases, the hematological data presented by the automated hemogram may be very similar in both entities, showing moderate anemia, microcytosis, and increased red blood cells. From a practical point of view, it may be important to make an "at-first sight" diagnosis using simple parameters that may readily be obtained from the hemogram or from the laboratory. We have assessed the usefulness of RDW (red cell distribution width), of the England-Fraser index and of free erythrocyte protoporphyrin determination in predicting iron deficiency anemia or beta-thalassemia trait. Our results suggest that the most accurate of these parameters is the England-Fraser index, but that a presumptive diagnosis of beta-thalassemia trait can correctly be made if RDW and FEP values are near normality.