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Define the terms "flagged" and "reflex test" as they pertain to automated hematology results.
When performing a CBC on an automated machine, a flagged result is an indication that a particular result has not met established laboratory criteria and must be reviewed. The laboratory technician may need to do further testing, or "reflex testing," on the patient's sample in order to verify the test results.
Describe the importance of maintaining competency in morphological identification.
Even with the wealth of information that may be derived from an analyzer, the blood smear remains a crucial diagnostic aid, and maintaining technologist competency in the identification of cellular abnormalities should be a priority in the laboratory.
List justifications for performing a manual morphology review.
requested by the physician, resulting from an abnormality in the CBC, a result was flagged by the hematology analyzer
List the steps in the performance of a peripheral blood smear examination.
LOW POWER (10X) SCAN:
determine overall staining quality, verify a good distribution of cells, find an optimal area for examination
HIGH POWER (40X) SCAN:
determine the WBC estimate (avg. of 10 fields), correlate this with the automated results, evaluate WBC morphology
OIL IMMERSION (100X) EXAMINATION:
perform a 100 WBC differential count, evaluate RBC morphology, perform a platelet estimate/evaluate platelet morphology, correct WBC count that contains nucleated RBCs
Identify normal red blood cell morphology on a peripheral smear.
cells are normochromic and normocytic, with no inclusions
List and define the terms referring to abnormal red cell distribution, and specify the particular clinical conditions associated with these abnormalities.
agglutination: an aggregation of red cells into random clusters or masses, as the result of an antigen-antibody reaction within the body
roleaux: a condition in which red cells appear as stacks of coins on the peripheral smear, as a result of elevated globulins or fibrinogen in the plasma (which makes the cells sticky).
List and define the terms referring to variation in red cell size, and specify the particular clinical conditions associated with these abnormalities.
normocytic: red cells are normal in size (7-8µm in diameter, MCV between 80 and 100fL)
macrocytic: red cells are abnormally large (9+µm, MCV 100+fL) due to megaloblastic anemia, acute blood loss, or alcoholism
microcytic: red cells are abnormally small (<6µm, MCV <80fL) due to iron deficiency anemia or thalassemia (hereditary anemia)
List and define the terms referring to variations in red cell color/hemoglobin content, and specify the particular clinical conditions associated with these abnormalities.
normochromic: red cells are normal in color (zone of pallor <3µm, MCHC 32-36%) due to an adequate amount of hemoglobin
hypochromic: red cells are low in color (zone of pallor >3µm, MCH <27pg, MCHC <32%) due to iron deficiency anemia, and sometimes sideroblastic anemias and lead poisoning.
hyperchromic: red cells exhibit a decreased or absent zone of pallor (MCHC >36%) due to a hemolytic anemia.
Define the term "target cell."
Target cells, or codocytes, appear on the peripheral blood as a result of increase in RBC surface membrane due to excess membrane cholesterol and phospholipid, and decreased cellular hemoglobin.
(seen in anemias, hemoglobinopathies, thalassemias, and liver disease)
Define the term "spherocyte."
Spherocytes have a reduced surface-to-volume ratio that results in a cell with no central pallor. The most detailed mechanism for sphering is the congenital condition known as hereditray spherocytosis (HS), which is due to a deficiency/dysfunction in the membrane proteins spectrin, ankyrin, band 3 and/or protein 4.2.
Define the term "ovalocyte."
Ovalocytes are egg-shaped and have a tendency to vary in their hemoglobin content. Megaloblastic anemia is characterized by macroovalocytes that may be 9µm or more in diameter and lack central pallor.
Define the term "elliptocyte."
Elliptocytes are pencil, rod, or cigar-shaped and hemoglobin appears to be concentrated on both ends of the cell. Hereditary elliptocytosis (HE) is an inherited condition with anywhere from 25 to 90% of all cells demonstrating the elliptical appearance.
Define the term "stomatocyte."
Stomatocytes have a central pallor which is slit- or mouth-like. The abnormal morphology resulting in the stomatocyte is thought to be the result of a membrane defect.
(seen in hydrocytosis and xerocytosis, where abnormalities in cation permeability lead to changes in red cell volume)
Describe the most common red blood cell inclusions and their composition, relating each inclusion to clinical conditions in which they may be found.
Howell-Jolly bodies: nuclear remnants containing DNA that are 1 to 2µm in size and appear singly or doubly on the periphery of the cell membrane (surgical splenectomy, thalassemic syndromes, sickle cell anemia, megaloblastic anemias)
basophilic stippling: ribosomal and mitochondrial remnants produce a fine blue dusting or coarse dots around the periphery of RBCs (alcoholism, thalassemia syndromes, megaloblastic anemias, arsenic intoxication, lead poisoning)
Pappenheimer bodies (siderotic granules when seen in a stain other than Wright-Giemsa): small, irregular magenta inclusions seen along the periphery of red cells (any condition with iron overloading, hemoglobinopathies, splenectomy)
Heinz bodies: resulting from denatured/precipitated hemoglobin (alpha thalassemic syndroms, G6PD deficiency, unstable hemoglobin syndromes)
Cabot rings: figure-8 conformations (megaloblastic anemias, dyserythropoiesis, homozygous thalassemia, postsplenectomy)
Describe normal platelet morphology and specify some platelet abnormalities seen in pathologic conditions.
Normal platelets measure 2-4µm across, with a discoid shape and even blue granules dispersed throughout a light-blue cytoplasm. Gross variation in platelet morphology may be seen in infiltrative disease of the bone marrow.
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