Erythrocytes: Red Blood Cells

Erythrocytes (red blood cells) are the most abundant cells in the blood. The process by which erythrocytes are generated from hematopoietic stem cells of the hematopoietic bone marrow is called erythropoiesis. The production of erythrocytes is stimulated or controlled by the hormone erythropoietin (EPO). It is produced in adults predominantly by endothelial cells (specialized flat cells lining the inside of blood vessels) in the kidney (85-90%) and 10-15% by hepatocytes (liver cells) in the liver.They serve to transport oxygen to various body tissues. The diameter of an erythrocyte is about 7.5 µm and its thickness is 2 µm at the edge and 1 µm in the center. The average life span of an erythrocyte is about 120 days.

The process

Material needed

  • 3 ml EDTA blood (determined as part of the small blood count); mix tubes thoroughly by swirling immediately after collection.

Preparation of the patient

  • Not necessary

Disruptive factors

  • None known

Standard values

Normal values Men Women
Erythrocytes (Ery) 4.8-5.9 million/μl blood 4.3-5.2 mio/μl blood
Hemoglobin (Hb) 140-180 g/l (14-18 g/dL); < 13 g/l (anemia). 120-160 g/l (12-16 g/dl); < 12 g/l (anemia)
MCH 28-32 pg 28-32 pg
MCV 85-95 fl (femtoliter = 10-15liter) 85-95 fl
MCHC 32-36 g/dL 32-36 g/dl
RDW 6-8 µm

Legend

  • Erythrocyte count – number of red blood cells important for oxygen transportPolyglobulia (synonym: erythrocytosis), i.e., increase of erythrocytes above the physiological normal value.
  • Hemoglobin (Hb) – red blood pigment.
  • MCH (engl. mean corpuscular hemoglobin) – mean corpuscular hemoglobin (= mean hemoglobin content per erythrocyte); is used to differentiate anemia (anemia) into hypo-, normo- and hyperchromic anemia.
  • MCV (engl. mean corpuscular volume) – mean erythrocyte individual volume; serves to differentiate into a micro-, normo- and macrocytic anemia.
    • MCV can be calculated from the hematocrit and the number of erythrocytes in the blood using the following formula: MCV = hematocrit / erythrocyte count.
    • Mathematically, MCV is related to two other parameters: MCV = MCH / MCHC.
    • Note: In elderly patients, many variations of MCV occur, so the possibility of pathogenetic assignment is difficult.

    Macrocytosis: mean corpuscular volume (MCV) of > 100 femtoliters with near normal hemoglobin concentration.

  • MCHC (mean corpuscular hemoglobin concentration) – mean corpuscular hemoglobin concentration: mean hemoglobin concentration of hematocrit (the red cell mass). (MCHC = hemoglobin / hematocrit, MCHC = MCH / MCV).
  • RDW (English “red cell distribution width”, erythrocyte spread width) – allows a statement about the variation of the erythrocyte size.

Anemia is differentiated by the volume of erythrocytes (MCV):

  • <80: microcytic anemia (anemia characterized by small erythrocytes (red blood cells)).
  • 80-100: normocytic anemia (anemia characterized by normal-sized erythrocytes).
  • > 100: macrocytic anemia (anemia characterized by enlarged erythrocytes).

RDW (“red cell distribution width”, red cell distribution width).

  • Increased RDW values
    • Indicate anisocytosis (unequal size distribution of normally equal-sized cells).
    • Are considered a risk factor for increased mortality (mortality) in elderly patients
  • Decreased RDW values are more often found in macro/microcytosis.

Red cell morphology

  • Basophilic spotting of erythrocytes: small basophilic granules in erythrocytes; occurrence in combination with microcytic anemia (MCV < 80); furthermore, in lead poisoning.
  • Dacrocytes (tear drop erythrocyte; English tear drop cell, dacryocyte; “teardrops”): deformation of erythrocytes to tear shape; typical causes include autoimmune hemolytic anemia (AIHA), myelofibrosis / osteomyelofibrosis myeloproliferative syndromes and bone marrow carcinomatosis.
  • Fragmentocytes or schistocytes: damaged erythrocytes or areal tears of them; when they appear, life-threatening thrombotic microangiopathies (disease of small blood vessels) – thrombotic thrombocytopenic purpura (TTP) or (atypical) hemolytic uremic syndrome (HUS) – should be excluded.
  • Money roll formation (pseudoagglutination): multiple causes such as high platelet counts and increased plasma proteins; disease with paraproteins such as multiple myeloma (plasmocytoma) is also possible; furthermore, cryoglobulinemia (belongs to the group of vasculitides (vascular inflammations)) can also lead to money roll. Note: cryoglobulins are found in numerous infectious and autoimmune diseases.
  • Megalocytes: enlarged oval erythrocytes (> 8 µm) that can typically develop in maturation disorders of erythropoiesis; typical causes are vitamin B12 deficiency (e.g., pernicious anemia) and folic acid deficiency; copper deficiency can also be a cause in rare cases. Other diseases associated with megalocytes include bone marrow diseases (e.g., myelodysplastic syndrome (MDS)), alcoholism, hypothyroidism (underactive thyroid), and liver disease.
  • Spherocytosis (spherocytic anemia), hereditary: heterogeneous group of diseases of erythrocytes; it shows normochromic, normocytic anemia (MCV: 80-100); the disease belongs to the congenital hemolytic anemias (forms of anemia in which red blood cells do not reach their normal lifespan).