In thalassemia microcytes exceed hypochromic cells. In iron deficiency, hypochromic cells exceed microcytes. The ratio of microcytes (M) to hypochromic cells (H) can help distinguish thalassemia from iron deficiency anemia.
Patient selection: presence of hypochromic anemia
Parameters (as originally determined on the Techinicon H*1 automated analyzer):
(1) M = percentage of cells that are microcytes (erythrocytes with volume less than 60 femtoliters)
(2) H = percentage of cells that are hypochromic (erythrocytes with hemoglobin less than 28 g/dL MCHC)
ratio =
= M / H
Interpretation:
• A ratio < 0.9 indicates iron deficiency.
• A ratio > 0.9 indicates thalassemia minor.
• A ratio = 0.9 is indeterminate.
Limitations:
• Mixed thalassemia minor and iron deficiency is relatively common.
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