The width of the red blood cell volume distribution is a parameter that reflects the heterogeneity of the red blood cell volume size, often as a coefficient of variation of the measured red blood cell volume size. It is a parameter that reflects the heterogeneity of the volume of peripheral blood erythrocytes obtained by hematology analyzer measurements. In short, it is an objective indicator of the heterogeneity of red blood cell size. The morphological classification of anemia is generally performed by two parameters, RDW and MCV. The diagnosis of increased red blood cell volume can be confirmed by the following tests: 1. Blood picture A small cell hypochromic anemia is present. The mean red blood cell volume (MCV) is less than 80 fl, the mean red blood cell hemoglobin content (MCH) is less than 27 pg, and the mean red blood cell hemoglobin concentration (MCHC) is less than 0,32. Small red blood cell bodies and enlarged central lightly stained areas are seen in blood films. Reticulocyte counts are mostly normal or mildly increased. White blood cell and platelet counts may be normal or reduced. Bone marrow picture: active or apparently active proliferation, mainly in the red lineage, with no obvious abnormalities in the granulocyte and megakaryocyte lineages; the red lineage is dominated by middle and late juvenile erythrocytes, with small size, dense nuclear chromatin, little cytoplasm and uneven margins, and poor hemoglobin formation (“old nucleus and young plasma”). 3, iron metabolism Bone marrow smear stained with potassium ferricyanide (Prussian reaction), no dark blue iron-containing heme particles in bone marrow granules, reduced or absent iron granules in young erythrocytes, less than 0,15 iron granule juvenile cells; decreased serum ferritin (<12μg/L); decreased serum iron (L), increased total iron binding capacity (>64,44μmol/L), decreased transferrin saturation (<15%). (<15%). sTfR (soluble transferrin receptor) concentration exceeds 8 mg/L. 4. Intraerythrocytic porphyrin metabolism FEP (erythrocyte free protoporphyrin) >0, 9 mmol/L (whole blood), ZPP (zinc protoporphyrin) >0, 96 mmol/L (whole blood), FEP/Hb (hemoglobin) >4, 5 mg/gHb.