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Uses

To detect the presence of abnormal hematologic cells such as schistocytes or blast cells in a peripheral blood smear as well as to observe the morphology of such cell lines and any abnormalities associated with them such as in the case of sickle cell disease.

Schistocytes are fragmented red blood cells due to shearing forces in microarterioles lined or meshed with fibrin strands. They are found in patients with disseminated intravascular coagulation, thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, microangiopathic hemolytic anemia, uremia, and carcinoma. Turbulent blood flow due to congestive heart failure, artificial heart valves, or valvular stenosis may cause schistocyte formation. Greater than 1% of forms or greater than two schistocytes per high-powered field suggests schistocytosis.

Peripheral blood smear blasts are circulating immature white blood cells. When elevated white blood cell count and circulating blasts are seen in addition to anemia and thrombocytopenia, acute leukemia is suspected. As leukemia blast cells build up in the bone marrow, they allow less room for production of healthy white blood cells, red blood cells, and platelets. Although the diagnosis of leukemia can usually be made from the peripheral smear, bone marrow examination (aspiration or needle biopsy) is routinely done for definitive diagnosis.

Materials

Two glass microscope slides, drop of blood, pipette, Wright stain, Giemsa stain, immersion oil, and microscope.

Method

Smear Preparation

  1. Agitate sample well, by inversion of tube or mechanical rocker.

  2. Place a 2- to 3-mm drop of whole blood ¼ inch from the right edge of a 1 × 3 inch slide using a wooden applicator stick.

  3. Place the slide on a flat surface and hold securely.

  4. Grasp a 2nd slide (spreader slide) in the right hand between thumb and forefinger.

  5. Place the spreader slide onto the lower slide in front of the blood drop, and pull the slide back until it touches the drop.

  6. Allow the blood to spread by capillary action almost to the edges of the lower slide.

  7. Push the spreader slide forward at a 30-degree angle, using a rapid even motion. The weight of the spreader slide should be the only weight applied. The drop of blood must be spread within seconds or the cell distribution will be uneven.

  8. Allow to air dry.

FIGURE 25.28

Schistocytes. Multiple fragmented red blood cells (black arrowheads) seen on the peripheral smear at ×100 in a patient with microangiopathic hemolytic anemia. (Photo contributor: James P. Elrod, MD, PhD.)

FIGURE 25.29

Acute Myeloid Leukemia (AML) Blast Cells. Wright stained peripheral blood smear, ×1000. Multiple blast cells seen in this smear from a patient with shortness of breath and a white blood cell count of 105 K/μL, 80% blasts, hematocrit 20%, and platelet count of 75 K/μL. Flow cytometry confirms these are myeloid blasts, ...

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