TERMINOLOGY FOR BLOOD WORK

Transcription

1 TERMINOLOGY FOR BLOOD WORK I. RBC (Red Blood Cell) CONSIDERATIONS A. Morphology 1. SIZE (anisocytotic, anisocytosis = variation in size (Gk. anisos = unequal)) a. Normal size is 6-8 m b. Microcytic is 0-5 m c. Macrocytic is m Note: Too much anisocytosis indicates pathology! 2. SHAPE (poikilocytotic, poikilocytosis = variation in shape (Gk. poiki = varied)) a. Burr cells (RBC membrane has kinks in it, looks like a burr) b. Tear drops c. Helmet d. Ovalocytes e. Elliptocytes 1. One stage to sickle cell shape 2. Sickled cells f. Spherocytes (No room for expansion within cell; very little tolerance for different blood tonicity as cells are already spherical. Spherocytosis is inherited.) B. Coloration 1. Polychromasia: when RBCs look bluish; indicative of young, immature cells. 2. Hypochromasia: characterized by a big, pale area in the center of RBC; indicative of too little hemoglobin. Note: microcytic hypochromasia is the classic irondeficient anemia. 3. Basophilic stippling: very abnormal; related to polychromasia seen with lead poisoning. 4. Howell-Jolly bodies; small, round or oval structures (pink or blue in color) observed in RBCs of various anemias and leukemia. These most probably represent little remnants of the nucleus (from reticulocytes) which become inclusions in the erythrocytes. C. Other 1. Nucleated RBCs: 1% of all RBCs being nucleated is very abnormal and is indicative of metarubricyte (or blast-form) being released prematurely from the myeloid. 2. Reticulocytes: immature RBCs. Retic counts are done to evaluate the erythropoietic rate and to monitor anemic treatments. Putman/Biol 242 Terms for Blood Work/ /Page 1

2 3. RBCs enter the circulation at the rate of 2 million per second (which equals the rate of RBC destruction). RBCs live about 120 days in circulation. II. WBC (White Blood Cell) CONSIDERATIONS A. Criteria for differentiating WBCs 1. Overall diameter of the cell: a. Platelets smallest b. RBCs larger than platelets c. Lymphocytes vary from just larger than to twice as large as RBCs as their morphology varies from well-contracted to amoeboid d. Basophils, neutrophils, eosinophils are all about equal in size and are nearly twice as large as RBCs. e. Monocytes are three times the size of RBCs. 2. Cytoplasmic granules a. Granules visible in cytoplasm (granulocytes): -neutrophils (very small, pink granules, or granules barely visible) -eosinophils (red granules) -basophil (blue granules) b. Granules not visible in cytoplasm (agranulocytes): -lymphocytes -monocytes 3. Morphology of the nucleus a. Large, generally round, dark bluish-purple nucleus: lymphocyte b. Largest, dinged, pinky-purple nucleus: monocyte c. Dark nucleus clearly visible, NOT round, but of uniform width or lobed: 1. Uniform width and shape like a c, n, s, or u = banded neutrophils or bands 2. The older the neutrophil gets (that is, the longer it is in circulation), the more segmented the nucleus gets. The once uniform nuclear material starts to attenuate (pull apart) and form lobes; but always a thin strand of nuclear material attaches one lobe to another. There may be as many as 7-8 lobes. Even with only two lobes, as soon as distinct lobes are visib le, the cells are called segmented neutrophils or segs. d. Dark nucleus is not distinctly visible; because it is masked by the cytoplasmic granules: 1. Nucleus completely covered by large, dark-blue granules = basophil. 2. Segmented nucleus is not totally obscured by large, orangy-red granules = neutrophil. Note: the visible nucleus is OFTEN (not always) segmented in such a way as to have two large lobes with a much smaller lobe in between. This is referred to as a spectacles nucleus for its obvious similarity to a pair of glasses. e. Overall color and texture (although this is the least reliable of the criteria because, over time, the coloration changes or the Wright s stain may be mixed a little differently one time than another. f. Neutrophils are referred to as PMNs (polymorphonuclearleucocytes) because of their high variation in nuclear morphologies. Putman/Biol 242 Terms for Blood Work/ /Page 2

3 B. WBC Diff-Count Terminology 1. Two suffixes denote increased numbers of something: a. philia (used for granulocytes: neutrophils, basophils & eosinophils neutrophilia = increased numbers of neutrophils basophilia = increased numbers of basophils eosinophilia = increased numbers of eosinophils b. cytosis (used for agranulocytes: lymphocytes, monocytes lymphocytosis = increased numbers of lymphocytes monocytosis = increased numbers of monocytes 2. One suffix denotes decreased numbers of something: -penia (Note usage below): neutropenia = decreased numbers of neutrophils basopenia = decreased numbers of basophils eosinopenia = decreased numbers of eosinophils lymphocytopenia = decreased numbers of lymphocytes monocytopenia = decreased numbers of monocytes Putman/Biol 242 Terms for Blood Work/ /Page 3

4 HUMAN BLOOD Erythrocytes (RBCs) of man and other mammals are non-nucleated when mature, unlike the erythrocytes of other vertebrates, which are nucleated. In order to differentiate between leucocytes (WBCs) you must stain them. Wright s stain is a mixture of eosin and hematoxyln. Eosinophils, as the name implies, strongly take up eosin, staining its large granules red; neutrophils take up eosin weakly, staining their smaller granules pink. Basophils take up hematoxyln, staining their large granules blue. Hematoxyln also stains nuclei, allowing us to examine nuclear morphology. Lymphocytes and monocytes have somewhat similar, circular nuclei; monocytes, however, have more cytoplasm surrounding the nucleus than do lymphocytes, and are much larger than lymphocytes. Neutrophils, eosinophils and basophily all have irregular nuclei. Normal human blood contains 4,500,000 to 5,000,000 erythrocytes and 5,000 to 9,000 leucocytes per cc of blood. The leucocytes and their clinically normal values (from nlm.nih.gov/medlineplus/ency/article/ htm) are as follows: Neutrophils 40 to 60% Lymphocytes 20 to 40% Monocytes 2 to 8% Eosinophils 1 to 4% Basophils 0.5 to 1% Function of Leucocytes and Diagnostic Significance of Percent Variations Some generalizations about what higher than normal levels of each leucocyte may suggest (from labtestsonline.org and nlm.nih.gov/medlineplus/ency/article/ htm). Leukemias will also increase populations of specific leucocytes. Neutrophils: Acute bacterial infections, tissue inflammation and necrosis, trauma. Some viral and fungal infections will also elevate neutrophil percentages. Lymphocytes: Infections in general will raise lymphocyte levels as the immune system is triggered and more lymphocytes are produced. Monocytes: Viral infections, inflammatory disease and parasitic infections may increase monocyte populations. Eosinophils: Parasitic infections, allergic reactions and cancers may increase eosinophil populations. Basophils: Inflammation and allergic reactions may increase basophils. CBC (Complete Blood Count) MEDICAL TESTS Putman/Biol 242 Terms for Blood Work/ /Page 4

5 Diagnostic Value: A valuable test that screens for anemia and various infections by assessing the white blood cell count, red blood cell count and platelet count. Procedure: The test is performed on a blood sample and consists of cell counting by a Coulter counter and blood smears for evaluating the white blood cells and red blood cells. Usually included are a determination of red blood cell count, hemoglobin, hematocrit, white blood cell count, differential white blood cell count and platelet count. Differential White Blood Cell Count Diagnostic Value: A routine part of the complete blood count (CBC) that may be helpful in evaluating infection or inflammation, determining the effects of possible poisoning by chemicals or drugs, monitoring blood disorders (e.g. leukemia) and effects of chemotherapy or detecting allergic reactions and parasitic infections. Procedure: A sample of blood is spread on a glass slide and stained. Then the percentage of each type of white blood cell is determined. Hematocrit or Hct Diagnostic Value: The hematocrit (htc) is the percentage of red blood cells in blood. A hematocrit of 40 means that 40% of the volume of blood is composed of red blood cells. The test is used to diagnose anemia and polycythemia (an increase in the percentage of the red blood cells) and abnormal states of hydration. Procedure: A sample of venous blood is loaded into a heparinized capillary tube and centrifuged, causing erythrocytes (and other formed elements) and plasma to separate. The height of the erythrocyte column is measured, along with the total height of the blood sample and the percentage of red blood cells to whole blood calculated. Normal values: Females: 38-46% (average 42%), males 40-54% (average 47%). A significant drop in htc constitutes anemia, which may vary from mild (htc 35%) to severe (htc < 15%). Polycythemic blood may have a htc of 65% or higher. Athletes not uncommonly have a higherthan-average htc, and the average htc of persons living in mountainous terrain is greater than that of persons living at sea level. Reticulocyte Count Diagnostic Value: To measure the rate of erythropoiesis and thus evaluate the bone marrow s response to anemia (low hemoglobin) or to monitor treatment for anemia. Procedure: A blood sample is stained and examined to determine the percentage of reticulocytes in the total number of red blood cells. Normal Values: %. A high reticulocyte count might indicate the response to bleeding, hemolysis (rapid breakdown of erythrocytes), or the response to iron therapy in someone who is Putman/Biol 242 Terms for Blood Work/ /Page 5

6 iron deficient. Low reticulocyte count in the presence of anemia might indicate inability of the bone marrow to respond, owing to a nutritional deficiency, pernicious anemia or leukemia. Summary of Physical Characteristics of Blood Viscosity Temperature 38 C (100.4 F) ph Salinity 0.90% Total body weight 8 liters Volume 5-6 L for average male, 4-5 L for average female Modified from H/O by Mary Bath-Balogh of Pierce College, Ft. Steilacoom Putman/Biol 242 Terms for Blood Work/ /Page 6