Before you can begin to abstract from the hematology reports, you must be aware of the terms you will encounter and of their significance. Following are definitions of terms which you will encounter frequently.

Red Blood Cells

There is only one type of mature erythrocyte (red blood cell), but there are several types of immature erythrocytes. One common type is called a reticulocyte.

Hemoglobin is a blood protein found in red blood cells; it transports oxygen to the tissues of the body and returns carbon dioxide to the lungs.

Hematocrit measures the volume of erythrocytes. It is expressed as a percentage of the volume of whole blood.

White Blood Cells

Leukocytes (white blood cells) are of two main types-granulocytes or granular leukocytes (containing granules in their cytoplasm) and agranular leukocytes (lacking granules in their cytoplasm).

Granulocytes or granular leukocytes can be further subdivided (based on the staining properties of the granules) into:

Neutrophils (purple) - 40-60% of all leukocytes
Eosinophils (red) - 1-3% of all leukocytes
Basophils (blue) - 0-1% of all leukocytes

A neutrophil may be further specified as segmented (SEGS), banded (STABS), or juvenile (a metamyelocyte).

A myelocyte is a granulocytic cell.

Agranular leukocytes may be further subdivided into two types:

Monocytes - 4-8% of all leukocytes
Lymphocytes - 20-40% of all leukocytes

Stem Cell


Platelets (thrombocytes) are tiny cells or discs whose primary function is hemostasis (clotting of blood).