Differential diagnosis of microcytic anemia: the role of microcytic and hypochromic erythrocytes

SUMMARY Introduction: Various indices derived from red blood cell (RBC) parameters have been described for distinguishing thalassemia and iron deficiency. We studied the microcytic to hypochromic RBC ratio as a discriminant index in microcytic anemia and compared it to traditional indices in a learning set and confirmed our findings in a validation set. Methods: The learning set comprised samples from 371 patients with microcytic anemia mean cell volume (MCV 6.4 was strongly indicative of thalassemia (area under the curve 0.948). Green-King and England-Fraser indices showed comparable area under the ROC curve. However, the microcytic to hypochro- mic ratio had the highest sensitivity (0.964). In the validation set, 91.1% of microcytic patients were correctly classified using the M/ H ratio. Conclusions: Overall, the microcytic to hypochromic ratio as measured in CELL-DYN Sapphire performed equally well as the Green-King index in identifying thalassemia carriers, but with higher sensitivity, making it a quick and inexpensive screening tool.