Color Atlas of Hematology - Practical Microscopic and Clinical ...

128Erythrocyte and Thrombocyte AbnormalitiesClinically Relevant Classification Principle for Anemias:Mean Erythrocyte Hemoglobin Content (MCH)In current diagnostic practice, erythrocyte count and hemoglobin content(grams per 100 ml) in whole blood are determined synchronously. This allowscalculation of the hemoglobin content per individual erythrocyte(mean corpuscular hemoglobin, MCH) using the following simple formula(p. 10):Hb (g/dl) · 10Ery (10 6 /µl)The mean cell volume, hematocrit, MCH, and erythrocyte size can be usedfor various calculations (Table 22; methods p. 10, normal values Table 2,p. 12). Despite this multiplicity of possible measures, however, in routinediagnostic practice the differential diagnosis in cases of low Hb concentrationor low erythrocyte counts relies above all on the MCH, and mostforms of anemia can safely be classified by reference to the normal datarange of 26–32 pg Hb/cell (1.61–1.99 fmol/cell) as normochromic (withinthe normal range), hypochromic (below the), or hyperchromic (above thenorm). The reticulocyte count (p. 11) provides important additionalpathophysiological information. Anemias with increased erythrocyte production(hyper-regenerative anemias) suggest a high reticulocyte count,while anemias with diminished erythrocyte production (hyporegenerativeanemias) have low reticulocyte counts (Table 22).It should be noted that hyporegenerative anemias due to iron or vitamindeficiency can rapidly display hyper-regeneration activity afteronly a short course of treatment with iron or vitamin supplements (up tothe desirable “reticulocyte crisis”).The practical classification of anemia starts with the MCH:— 26–32 pg = normochromic— Less than 26 pg = hypochromic— More than 32 pg = hyperchromicHypochromic AnemiasIron Deficiency AnemiaMost anemias are hypochromic. Their usual cause is iron deficiency fromvarious causes (Fig. 44). To distinguish quickly between real iron deficiencyand an iron distribution disorder, iron and ferritin levels should bedetermined.