Normoblasts

Normoblasts
Appearance:

Normoblasts are the nucleated precursors of erythrocytes. The cytoplasm changes with the increasing maturity from basophilic, to polychromatophilic to orthochromatic. The nucleus is coarse to pycnotic, compact and partially eccentric.
Counting:
In peripheral blood, the normoblast count is calculated relative to 100 leukocytes. If more than 3-5 normoblasts per 100 leukocytes are found, the white blood count must be corrected (correction for normoblasts).

Correction for normoblasts:
Calculation:
Corrected leukocyte count
=
Automatically-counted leukocytes

100 + microscopically-counted normoblasts
x 100
Example:
Corrected leukocyte count at 15 normoblastes/100 leukocytes
=
47.7 x 109/L

100 + 15
x 100 = 41.5 x 109/L

Occurrence:
The occurrence of normoblasts in the peripheral blood is always pathological. They can be observed in accelerated erythropoiesis (e.g. in severe hemolysis), in bone marrow metastatic disease, or in extramedullary blood formation.