1% to 10%
4% to 14%
20% to 44%
18% to 38%
4% to 10%
1% to 12%
0% to 4%
1% to 4%
0% to 2%
5,000 X 100/110 = 4545.50 The corrected white count is 4545.50.
Recording RBC Morphology
1. Scan area using X100 (oil immersion).
2. Observe 10 fields.
3. Red cells are observed for size, color, hemoglobin content or pallor, and shape.
4. Normal morphology a. Normocytic: normal cell size and shape b. Normochromic: normal hemoglobin content and color
5. Abnormal morphology: Red cell morphology is assessed according to size, shape, hemoglobin content, and the presence or absence of inclusions. See the following sample grading system. Note that red cell morphology must be scanned in a good counting area. Two questions should be asked, Is the morphology seen in every field? Is the morphology pathologic and not artificially induced? Table 20.4 represents a system derived to determine a quantitative scale.
a. Report RBC size (see Table 20.5 for a composite list of red cell morphologies matched to clinical conditions). Anisocytosis is a term meaning variation in the size of the RBCs. The average size of an RBC is 7.2 pm with a range of 6.8 to 7.5 pm.
• Normocyte: normal size of RBC
• Macrocyte: larger than the normal RBC (>8.2 pm) and is the result of a defect in nuclear maturation or stimulated ery-thropoiesis
• Microcytic: smaller than the normal RBC, <7.2 pm, and is associated with a decrease in hemoglobin synthesis b. Shape. Poikilocytosis is the general term for mature erythrocytes that have a shape other than the round, biconcave disk. Poikilo-cytes can be seen in many shapes.
• Acanthocyte: thorny projections that are irregularly distributed around the red cell and lack an area of a central pallor.
• Burr cell (echinocyte): short and spikelike projections that are evenly distributed around the cell membrane.
• Ovalocyte (elliptocyte): an elongated oval cell. They are a result of a membrane defect.
308 PartV • Laboratory Procedures
• Schistocyte: red cell fragments that are irregular in shape and size. They are usually half the size of the normal RBC; therefore, they have a deeper red color.
• Sickle cells: crescent shaped with usually one end pointed. They can vary in size but are usually smaller than the normal RBC. These occur due to a decrease in oxygen and decrease in pH.
• Spherocyte: red cells that lack the central pallor or the biconcave disk. Usually they are smaller (<6 pm) and appear darker from the red cell background. They can appear as artifacts if the slide is examined in too thin of an area.
• Stomatocyte: Red cell with a slit-like central pallor that resembles a mouth. These are the result of increased sodium ions and decreased potassium ion concentration within the cytoplasm of RBCs.
• Target cell: Red cell with a "target" or bull's-eye appearance. The cell appears with a central bull's eye that is surrounded by a clear ring and then an outer red ring.
• Teardrop: resembles a tear and usually smaller than the normal RBC.
c. Variation in erythrocyte color. A normal erythrocyte has a pinkish-red color with a slightly lighter-colored center (central pallor) when stained with a blood stain, such as Wright. The color of the erythrocyte is representative of hemoglobin concentration in the cell. Under normal conditions, when the color, central pallor, and hemoglobin are proportional, the erythrocyte is referred to as normochromic. To grade color variations, use the method described in Table 20.5.
• Hypochromia: increased central pallor and decreased hemoglobin concentration.
• Polychromasia: is used to describe ery-throcytes that have a faint blue-orange color and those that are slightly larger than normal red cells.
d. Inclusions. There are several inclusions that can be seen in erythrocytes and/or white cells. Use Table 20.6 for grading inclusions. Inclusions are listed in alphabetical order.
Auer rods are aggregates of fused lyso-somes, appearing as red needle-like inclusions. They are found in WBCs and are pathological. Basophilic stippling is tiny round granules that stain deep blue with Wright's stain. They are evenly distributed throughout the red cell and are composed of ribosomes and RNA. They do not occur in vivo but only on the smear. Cabot rings are delicate thread-like inclusions in the RBC. They can take on a variety of shapes such as a ring, figure-of-eight, or twisted. Döhle bodies are light blue-staining inclusions found in Wright-stained blood smears. They are usually observed in the periphery of the cytoplasm of neutrophils. Döhle bodies are aggregates of rough endoplasmic reticulum (RNA). Hemoglobin C crystals are found in blood smears that are normochromic and normocytic with at least 50% target cells. The shape of the C crystal is usually oblong in homozygous conditions. In hemoglobin SC disease, the hemoglobin C crystal is shaped like a gloved hand. Heinz body inclusions can either be round or irregularly shaped. They are made of denatured hemoglobin. These inclusions tend to lie close to the periphery of the cell. Observation of these inclusions is seen with supravital stains such as Brilliant Cresyl Blue or Crystal Violet. They are NOT observed on Wright's stain. Howell-Jolly bodies are round, dark-staining nuclear remnants of DNA. When present, there is only one or two per red cell.
Pappenheimer bodies (siderocytes) are seen as small dark-blue or purple dots in clusters along the periphery of the red cells in Wright stain. They are a result of a defect of iron and aggregated with mitochondria and ribosomes. Proof of these inclusions is done with a Prussian blue stain. See Table 20.7 for a composite of inclusions matched to disease states. Toxic granulation is an increased number of primary granules with intensified coloring. These can be found in segmented neutrophils and band forms.
UNOPETTE WHITE BLOOD CELL/PLATELET COUNT
The Unopette system is a system of prefilled blood dilution vials containing solutions that will preserve certain cell types while lysing others. Capillary pipettes are available to draw up different volumes of blood. The dilution is determined by the type of capillary used. The diluted blood is added to a hematocytometer chamber,
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