Clinical Pathology: Hematology PDF

Clinical Pathology: Hematology 3 CHA P TE R Patricia A. Schenck...

Clinical Pathology: Hematology 3 CHA P TE R Patricia A. Schenck VIII. Red cell distribution width (RDW) describes the COMPLETE BLOOD COUNT (REQUIRES relative width of the size distribution curve of SAMPLE COLLECTED INTO AN EDTA TUBE) the RBCs I. Packed cell volume (PCV) IX. Platelet concentration A. Percentage of whole blood composed of red A. In most species, platelets are much smaller blood cells (RBCs) than RBCs B. Collect in microhematocrit tube and centrifuge in B. In cats, platelet volume is about twice that of a microhematocrit centrifuge. Three layers will be most other species. Macroplatelets are also com- formed: mon in cats with hematology disorders and may 1. Plasma column at the top be counted as RBCs with particle-size analyzers 2. Erythrocytes at the bottom X. Blood smear 3. Buffy-coat layer in between the plasma and A. The counting area is the small area between the erythrocytes. The buffy coat layer is a small feathered edge and the thick portion of the white band containing leukocytes and plate- smear. The feathered edge should be observed lets. It may be red if many nucleated RBCs are for platelet clumps, large cells, and microfilaria present B. Reticulocyte count evaluates regeneration. A re- II. RBC count is performed by instruments designed for ticulocyte count should be performed if the PCV particle counting. It generally parallels the PCV and is below 30% in dogs or below 20% in cats hemoglobin concentration 1. Reticulocytes are evaluated with methylene III. Plasma protein concentration is determined by re- blue staining fractometry typically. Hyperlipemia can falsely in- 2. A corrected percentage for a reticulocyte value crease the plasma protein concentration by 2 g/dL greater than 1% or a count of greater than IV. Total leukocyte concentration 60,000 cells/ L indicates RBC regeneration. Re- A. Done by either Unopette dilution or by instru- generation takes at least 3 days before reticulo- ments designed for particle counting cytes appear in the circulation B. Both methods detect all nuclei in solution; thus 3. Horses do not release reticulocytes nucleated RBCs will be included in this count C. Morphology of RBCs V. Hemoglobin concentration is an index of the RBC 1. Changes in size mass per unit volume of blood a. Anisocytosis is variation in RBC size A. Provides information similar to that of PCV b. Microcytic RBCs are smaller than normal B. In most species (other than the camel family), RBCs, with a decreased MCV hemoglobin concentration is about a third of c. Macrocytic RBCs are larger than normal the PCV RBCs, with an increased MCV VI. Mean cell volume (MCV) reflects RBC size 2. Changes in shape (poikilocytosis) A. Macrocytic suggests increased red cell turnover. a. Poikilocytes are abnormally shaped RBCs Some toy poodles, miniature poodles, and grey- b. Schistocytes are RBC fragments usually hounds normally have macrocytic RBCs caused by intravascular trauma (i.e., DIC). B. Microcytic suggests defective red cell growth. When two or more spicules are present, the Akita and Shiba Inu dogs normally have micro- cells are called keratocytes cytic RBCs c. Acanthocytes (spur cells) are irregular, spic- C. Normocytic means red cell size is unchanged ulated RBCs with unevenly distributed sur- D. Comparing most species, dogs have the highest face projections (Figure 3-1) MCV values (largest RBCs), whereas sheep, (1) May result from changes in cholesterol llamas, and goats have the lowest MCV values or phospholipid concentrations in the (smallest RBCs) RBC membrane VII. Mean corpuscular hemoglobin (MCH) and mean cor- (2) Acanthocytes are commonly seen in puscular hemoglobin concentration (MCHC) help cats with hepatic lipidosis and dogs classify anemia with hemangiosarcoma 24  CHAPTER 3 Clinical Pathology: Hematology 25 b. Hypochromic RBCs are pale and have a de- creased hemoglobin concentration, usually from iron deficiency 4. Structures in or on RBCs a. Heinz bodies are caused by oxidant damage to RBCs, with denaturation of hemoglobin. Heinz bodies appear as small, pale struc- tures near the margin of the RBCs, which may protrude. With methylene blue stain- ing, these appear blue b. Basophilic stippling is caused by aggrega- tion of ribosomes into small granules. It is associated with immature RBCs in rumi- nants. Lead poisoning often causes baso- philic stippling c. Nucleated RBCs are RBCs in the peripheral Figure 3-1 Acanthocytes demonstrating irregularly sized spicules in a circulation that have retained their nucleus. blood smear from a dog with cholestatic liver disease. Wright’s stain, origi- nal magnification 132. (From Cowell RL et al. Diagnostic Cytology and They are an indication of regenerative ane- Hematology of the Dog and Cat, 3rd ed. St Louis, 2007, Mosby.) mia, a nonfunctioning spleen, or steroids (endogenous or exogenous) d. Howell-Jolly bodies are nuclear remnants in RBCs that appear as dark staining, round in- d. Echinocytes (burr cells) are spiculated clusions. They are associated with regenera- RBCs with evenly distributed blunt to sharp tive anemia or suppressed splenic function surface projections e. Siderotic granules are visible iron granules (1) May be artifactual from slow drying of in RBCs (siderocytes). They are associated blood smear with chloramphenicol, myelodysplasia, and (2) Have been observed in renal disease, impaired heme synthesis lymphoma, rattlesnake envenomation, f. Viral inclusions are rarely seen but may be and chemotherapy. Also observed after seen in canine distemper. They are most exercise in horses commonly found in polychromatic RBCs e. Spherocytes are dark-staining RBCs that lack g. Parasites (see later) central pallor. They are easiest to detect in 5. Rouleaux formation is the stacking of RBCs. This the dog because dog RBCs have the most is normal in horses and is enhanced when plasma central pallor normally. Their presence protein concentration is increased (Figure 3-2) suggests immune mediated hemolytic 6. Agglutination results in clumps of RBCs and is anemia associated with immune-mediated hemolytic f. Eccentrocytes are characterized by a shifting anemia (see Figure 3-2) of the hemoglobin concentration to one D. Leukocytes side, resulting in a loss of central pallor 1. Neutrophils with a clear eccentric zone. They are associ- a. Neutrophils have small granules in the cyto- ated with oxidative damage and may occur plasm that stain differently, depending on in conjunction with Heinz bodies species. In cows, these granules stain faintly g. Leptocytes are RBCs in which there is excess pink, giving the cytoplasm a pink tint membrane relative to internal contents. b. Neutrophils are important in an inflamma- These may occur in vitro when cells contact tory response with chemoattraction to the excess EDTA. Membrane folding causes tar- site of inflammation and phagocytosis of or- get cell formation (codocytes) ganisms or foreign material h. Codocytes are thin and bowl-shaped with a dense central area of hemoglobin (the ap- pearance of a target). They may be seen in animals with increased serum cholesterol Rouleau concentrations but have little significance i. Stomatocytes are RBCs with a mouthlike clear area in the center of the cell. Found in dogs with hereditary stomatocytosis 3. Changes in color Agglutination a. Polychromasia indicates the presence of young erythrocytes, polychromatophilic cells characterized by being larger and Figure 3-2 The pattern of erythrocyte adhesion that occurs with rouleau slightly bluer than mature RBCs. The degree is compared with the pattern that occurs with agglutination. (From Meyer D, of polychromasia correlates to the reticulo- Harvey JW. Veterinary Laboratory Medicine: Interpretation and Diagnosis, cyte response 3rd ed. St Louis, 2004, Saunders.) 26 SECTION I GENERAL DISCIPLINES IN VETERINARY MEDICINE c. Metamyelocytes are not normally present in 2. Normocytic anemia occurs when RBCs are of peripheral blood. They have a bean-shaped normal volume (normal MCV) nucleus 3. Macrocytic anemia occurs when RBCs are d. Band cells may be present normally in small larger than normal (increased MCV), indicating numbers. They have a characteristic that the marrow is releasing immature cells horseshoe-shaped nucleus B. Mean corpuscular hemoglobin concentration e. Segmented (mature) neutrophils normally (MCHC) predominate in peripheral blood 1. Hypochromic anemias are conditions where 2. Lymphocytes the RBCs contain less hemoglobin than normal a. Responsible for humoral immunity, cell- (decreased MCHC) mediated immunity, and cytokine responses 2. Normochromic anemias are conditions where b. Round to oval nucleus with minimal clear the RBCs contain a normal amount of hemoglo- cytoplasm bin (normal MCHC) c. Normal lymphocytes have smaller diameter 3. Hyperchromic anemias do not occur. MCHC than neutrophils. In ruminants, lympho- can be falsely elevated when intravascular he- cytes are more irregular in size and may be molysis is present the same size as neutrophils II. Responsiveness of bone marrow d. Reactive lymphocytes are probably B lym- A. Classified as regenerative or nonregenerative, phocytes producing immunoglobulin. They based on the number of immature RBCs that have a basophilic cytoplasm with irregular circulate nuclear shape. Nucleus may be indented, B. Regenerative anemia indicates that there are in- giving it a bean-appearance creased numbers of immature RBCs in the circula- e. Granular lymphocytes may be natural killer tion. An increase in immature RBCs is seen within or T cells and contain a small number of 2 to 4 days after blood loss or destruction. In re- pink-purple granules. More prominent in ru- generative anemia, the reticulocyte concentration minant blood is greater than 60,000 cells/ L. Horses typically do 3. Monocytes not release reticulocytes into the circulation a. Participate in the inflammatory response. 1. From blood loss Monocytes migrate into tissues and develop a. Acute blood loss into macrophages (1) Acanthocytes and schistocytes are usu- b. Commonly misidentified on a blood smear ally seen with hemangiosarcoma c. Nucleus may be oval, bean-shaped, or seg- (2) Typically see reticulocytosis, polychro- mented masia, and thrombocytopenia d. Larger diameter and grayer coloration to b. Chronic blood loss the cytoplasm than neutrophils. Cytoplasm (1) Results in iron deficiency anemia may contain fine light purple granules (2) Decreased MCV (microcytosis), in- 4. Eosinophils creased RDW, MCHC usually normal. a. Function not well understood. Contain pro- Keratocytes and schistocytes are teins that bind to parasite membranes and common are also involved in allergic responses 2. From destruction of blood b. Vary in morphology among species. All have a. Immune-mediated hemolytic anemia. prominent red to orange cytoplasmic gran- Spherocytes are common ules. Granules are rod- or barrel-shaped in b. Neonatal isoerythrolysis cat eosinophils. Granules may wash out c. Erythrocyte parasites during staining, leaving empty vacuoles; (1) Mycoplasma haemofelis (cats), Myco- this is most commonly seen in greyhounds plasma haemocanis (dogs), Mycoplasma 5. Basophils wenyonii (cattle), Mycoplasma haemo- a. Function is unknown. Basophils contain his- suis (swine), Candidatus Mycoplasma tamine and heparin, and their membrane haemolamae (llamas and alpacas). Ad- has bound IgE here to surface of the RBC membrane b. Normally not found on a blood smear (2) Anaplasma marginale (cattle), Anaplasma c. Larger than neutrophils, with a segmented centrale (cattle), Anaplasma ovis (sheep nucleus and dark-violet granules in the cyto- and goats). Dark blue inclusions in RBCs plasm. Cat basophils have large, faint gray (3) Babesia canis (dogs), Babesia gibsoni cytoplasmic granules (dogs), Babesia bovis (cattle), Babesia bigemina (cattle), Babesia equi and Babesia caballi (horses), Babesia ovis CLASSIFICATION OF ANEMIA and B. motasi (sheep), and B. cati, B. felis, I. Erythrocyte volume and hemoglobin concentration B. herpailuri, B. pantherae (cats). Single A. Mean corpuscular volume (MCV) or paired RBC inclusions 1. Microcytic anemia occurs when RBCs are small (4) Theileria parva and Theileria annulata (decreased MCV), usually because of iron defi- (cattle), Theileria lestoquardi (sheep and ciency or sometimes portocaval shunts goats). Signet-ring or comma-shaped  CHAPTER 3 Clinical Pathology: Hematology 27 (5) Cytauxzoon felis (cats). Signet-ring B. Primary (primary erythrocytosis) shaped inclusions 1. Bone marrow disorder d. Heinz body anemia. Caused by oxidant dam- 2. Cells appear normal, and maturation process is age to RBCs, with denaturation of hemoglo- normal bin. Heinz bodies appear as small, pale structures near the margin of the RBCs, LEUKOCYTE RESPONSES which may protrude. With methylene-blue staining, these appear blue I. Terminology (1) Plant ingestion: Allium (onions and gar- A. –philia as a suffix refers to an increase of that cell lic), Brassica (cabbage, kale, rapeseed), type red maple leaves (Acer rubrum) B. –penia as a suffix refers to a decrease of that cell (2) Chemical ingestion: Acetaminophen type (cats), propylene glycol (cats), zinc, C. Left shift is an increased concentration of imma- copper, methylene blue, crude oil ture neutrophils in the peripheral circulation. (birds) This can include band neutrophils, metamyelo- (3) Selenium deficiency (ruminants) cytes, or other early forms (4) Diabetes mellitus (cats) 1. Left shift with neutrophilia suggests inflamma- e. Hypophosphatemia tion (1) Postparturient hemoglobinuria (cattle) 2. Left shift with neutropenia indicates an aggres- (2) Diabetes mellitus (cats) sive inflammation with severe consumption of (3) Enteral feeding (especially cats) neutrophils f. Bacteria (Clostridium, Leptospira) D. Leukemia is the presence of neoplastic cells in g. Viruses (equine infectious anemia) the peripheral circulation h. Water intoxication (calves) E. Proliferative disorder refers to a blood cell neopla- i. Membrane defects: Hereditary spherocyto- sia that is present in blood, bone marrow, or tis- sis, hereditary stomatocytosis sues j. Metabolic defects: Pyruvate kinase defi- 1. Lymphoproliferative disorders are neoplasias of ciency, phosphofructokinase deficiency, lymphocytes. Lymphosarcoma (lymphoma) re- glucose-6-phosphate dehydrogenase fers to neoplasia of lymphocytes within tissue. deficiency, hereditary methemoglobinemia, Lymphocytic leukemia is neoplasia within porphyries bone marrow and blood C. Nonregenerative anemia is characterized by a 2. Myeloproliferative disorders originate from stem lack of immature RBCs when anemia is present cells in the bone marrow and provides evidence for bone marrow dysfunc- II. Changes in morphology tion. Most are normocytic A. Toxic change 1. Aplastic anemia (from infectious agents, tox- 1. Neutrophils have normal function ins, drugs, or estrogen) 2. Neutrophils are produced at an accelerated 2. Pure red cell aplasia (decreased erythroid pre- rate in the bone marrow as a response to in- cursors in bone marrow) flammation 3. Red cell hypoplasia (outside the bone mar- 3. Cytoplasm is basophilic due to increased ribo- row). Causes include inflammatory disease, some content chronic renal failure, endocrine disease, and 4. Döhle bodies may be present in cytoplasm. nutritional deficiencies These are aggregates of endoplasmic reticulum and are more commonly seen in cats 5. Cytoplasmic vacuolation may occur POLYCYTHEMIAS B. Hypersegmentation of neutrophil nuclei occurs I. Increase in concentration of erythrocytes in the when neutrophils are retained in the peripheral blood. Increased PCV, increased RBC count, in- circulation for a longer than normal time. This oc- creased hemoglobin concentration. The term erythro- curs in response to steroids cytosis is more accurate C. Degeneration of neutrophils is an artifact in blood II. Relative polycythemia that has aged for greater than 12 hours before A. Dehydration making a blood smear. Cytoplasmic vacuolation 1. Also see an increase in plasma proteins usually and nuclear swelling are noted 2. May have normal or low plasma proteins de- D. Leukocyte agglutination occurs in vitro. It may pending on underlying conditions cause a falsely low white blood cell (WBC) con- B. Splenic contraction centration. 1. Causes a mild increase in PCV (not greater E. Lymphocyte vacuolation may occur after inges- than 60%) tion of swainsonine (locoweed ingestion in horses 2. May be secondary to excitement or exercise or cattle). It also occurs in lysosomal storage dis- III. Absolute polycythemia eases A. Secondary III. Response to inflammation 1. Generalized hypoxia A. In inflammation there is an increased demand for 2. Increased erythropoietin production leukocytes as a result of consumption, and the 28 SECTION I GENERAL DISCIPLINES IN VETERINARY MEDICINE bone marrow should respond by releasing more a. Typically accompanied by nonregenerative leukocytes and increasing production anemia and thrombocytopenia B. Most inflammation is associated with some de- b. Causes include chemotherapeutic agents, gree of neutrophilia. The severity of the inflamma- other drugs such as estrogen or phenylbu- tion can be predicted by the degree of left shift tazone in dogs, and ehrlichiosis and the toxic changes present 2. Irreversible. Causes include feline leukemia vi- C. Neutropenia with left shift may occur when the rus (FeLV), hypoproliferative disorders, myelo- consumption of neutrophils by the inflammatory dysplasias, and myeloproliferative disorders process exceeds the bone marrow’s capacity to C. Approach to neutropenia produce neutrophils 1. Determine whether also anemic. If so, then D. There is species variation in the amount of bone consider chronic bone marrow injury marrow reserve to respond to inflammation. Dogs 2. If not anemic, then examine for left shift. If left have a high marrow reserve and can respond shift is present, consider acute inflammation with a significant neutrophilia. Cattle have limited 3. If there is no left shift, consider acute viral in- bone marrow reserve, and cats and horses have fection or acute marrow injury an intermediate reserve IX. Lymphopenia IV. Excitement response A. Usually due to steroids A. Caused by epinephrine release, which shifts B. In Arabian foals, it may indicate an inherited se- leukocytes from marginated pool to the circulat- vere deficiency of lymphocytes ing pool X. Monocytosis B. Absence of a left shift A. Relatively unimportant C. Recognized most frequently in cats, with lympho- B. Response to increased demand for macrophages cytosis up to about 20,000 cells/ L in tissues V. Stress response XI. Eosinophilia A. Caused by a release of adrenocorticotrophic A. Nonspecific response hormone (ACTH) causing increased cortisol B. Consider parasitism or hypersensitivity concentration XII. Basophilia B. Occurs with major systemic illness, pain, and A. Uncommon metabolic disturbances B. Interpretation unknown C. Lymphopenia is common D. Numbers of neutrophils are often doubled as a re- BONE MARROW EVALUATION sult of longer retention in the circulation. Hyper- segmentation of neutrophils may be seen. There I. Sites for collection is no left shift A. Dogs: Proximal end of the femur at the trochanteric E. Eosinopenia is often observed. Monocytosis usu- fossa, the iliac crest, proximal humerus (Figure 3-3) ally occurs in dogs B. Cats: Trochanteric fossa and humerus F. If a steroid response is not present in a sick dog, C. Horses, cattle, camelids: Ilium, ribs, or sternum hypoadrenocorticism should be suspected II. Indications VI. Approach to neutrophilia A. Nonregenerative anemia, neutropenia, thrombo- A. Determine whether left shift is present. If a left cytopenia, gammopathies, and possible neoplas- shift is present, suspect inflammation tic marrow disease B. If there is no left shift, then look at lymphocyte B. In horses, bone marrow evaluation helps deter- numbers. If there is lymphopenia, consider a ste- mine whether anemia is regenerative because roid response or possibly a steroid response com- horses do not release reticulocytes bined with inflammation III. Erythroid cells (derived from stem cells) C. If lymphocytes are normal or slightly increased, A. Erythroid cells have round nuclei and moderate consider an excitement response to deep blue cytoplasm that becomes pinker as VII. Lymphocytosis hemoglobin is produced A. Excitement response. Lymphocytes are normal B. Maturation sequence (immature to mature): Rubri- appearing blast, prorubricyte, rubricyte, metarubricyte, poly- B. Lymphocytic leukemia chromatophilic erythrocyte, mature erythrocyte 1. Abnormal morphology includes a large-diameter, C. Rubriblasts are the largest of the erythroid lighter-staining nucleus, visible nucleoli, and in- series, with round nuclei, slightly coarse chroma- creased amount of cytoplasm tin, and nucleoli. There is little cytoplasm that 2. Bovine leukemia virus with persistent lympho- stains dark blue cytosis D. Prorubricytes do not have nucleoli, are smaller C. Chronic canine ehrlichiosis than rubriblasts, and have a little more cytoplasm VIII. Neutropenia E. Rubricytes can still undergo mitosis, are smaller A. Acute inflammatory consumption is accompanied than prorubricytes, have very coarse chromatin, by a left shift. Toxic neutrophil changes occur and polychromatophilic cytoplasm within a few days F. Metarubricytes still contain a nucleus, are smaller B. Stem cell injury than rubricytes, and have polychromatophilic 1. Reversible cytoplasm  CHAPTER 3 Clinical Pathology: Hematology 29 A B C Figure 3-3 Dog skeleton showing common sites for bone marrow collection. In large dogs, the dorsal approach to the iliac crest (A) is an excellent site for aspiration and core biopsies. In small dogs and cats the lateral approach to the wing of the ilium (A) is a good site for core biopsies, and the trochanter fossa of proximal femur (B) is a good site for aspiration biopsies. For all small animals, the proximal humerus (C) is an excellent site for both aspiration and core bi- opsies. (Reprinted with permission from Grindem CD, Neel JA, Juopperi TA. Cytology of bone marrow. Vet Clin Small Anim 32:1316, 2002.) G. Polychromatophilic erythrocytes do not contain a VI. Megakaryocyte cells (derived from stem cells) nucleus, are blue-pink, and may contain nuclear A. Maturation sequence (immature to mature): remnants (Howell-Jolly bodies). When stained Megakaryoblasts, promegakaryocytes, megakary- with methylene blue and reticulum is visible, they ocytes are termed reticulocytes B. Megakaryoblasts are larger than any other types IV. Granulocyte (myeloid) cells (derived from stem of precursors cells) C. Promegakaryocytes have two to four nuclei with A. Granulocytes have irregularly shaped nuclei with a deep blue cytoplasm fine chromatin patterns and lavender cytoplasm D. Megakaryocytes are very large, with numerous B. Maturation sequence (immature to mature): My- nuclei that are connected. The cytoplasm be- eloblast, promyelocyte, myelocyte, metamyelo- comes granular and is sometimes light pink cyte, band neutrophil, segmented neutrophil VII. Other cells C. Type I myeloblasts are the most immature, with a A. Lymphocytes appear as they do in the peripheral round to oval nucleus, nucleoli, small amount of circulation blue-staining cytoplasm, and no azurophilic gran- B. Plasma cells are differentiated lymphocytes that ules. The cytoplasm has a ground glass appear- produce immunoglobulin. They look similar to ru- ance and may contain small vacuoles bricytes, but the cytoplasm is more abundant in D. Type II myeloblasts contain a few azurophilic plasma cells and they have a clear perinuclear granules (primary granules) in the cytoplasm; Golgi zone otherwise appear similar to type I myeloblasts C. Lymphoblasts are rare, and their presence may E. Promyelocytes have many azurophilic granules in indicate a lymphoproliferative disorder the cytoplasm; the nucleus is central to eccentric, D. Macrophages and nucleoli are present 1. Derived from monocytes F. Myelocytes can still undergo mitosis, are smaller 2. In low numbers in bone marrow than promyelocytes, have light blue cytoplasm, 3. Cytoplasm is usually vacuolated, is gray-blue, have no primary granules, and nuclei are round and may contain small pink granules to oval. Secondary granules are present, so eosin- 4. Macrophages phagocytize debris and often ophilic precursors contain pink granules, and ba- contain hemosiderin sophilic precursors contain purple granules E. Osteoblasts and osteoclasts G. Metamyelocytes have kidney-bean–shaped nuclei, 1. Osteoblasts appear similar to plasma cells but and are smaller than myelocytes are larger H. Band neutrophils have horseshoe-shaped nuclei, 2. Osteoclasts appear similar to megakaryocytes, with cytoplasm similar to segmented neutrophils but their nuclei are individual. Osteoclasts are V. Monocyte cells (derived from stem cells) specialized macrophages that lyse bone A. Difficult to distinguish from myeloid series. Mono- F. Mast cells are rare, large round cells with many cyte cells have irregular nuclear outlines metachromatic granules in the cytoplasm B. Maturation sequence (immature to mature): VIII. Interpretation Monoblasts, promonocytes, monocytes A. Cellularity C. Monocytes in bone marrow appear the same in 1. Normal marrow is about 50% cells and 50% fat peripheral blood. Precursors are difficult to iden- 2. Hemodiluted samples are difficult to tify unless there is a monocytic leukemia evaluate 30 SECTION I GENERAL DISCIPLINES IN VETERINARY MEDICINE Box 3-1 Normal Myeloid and Erythroid Maturation Myeloid Series Maturation Pyramid Erythroid Series Myeloblasts Rubriblasts ( 5% of AMC) ( 5% of AEC) Blasts Proliferative pool Maturation & storage pool Progranulocytes, Prorubricytes, rubri- myelocytes (⬃15% of cytes (⬃65%-75% AEC) AMC) Metamyelocytes, bands, Metarubricytes segmented neutrophils (⬃20%-30% AEC) (⬃80%-85% AMC) Cowell, RL, et al. Diagnostic Cytology and Hematology of the Dog and Cat, 3rd ed. St Louis, 2007, Mosby. B. Megakaryocytes: Should be at least 5 to 10 mega- E. Macrophages are usually present in small num- karyocytes per slide bers. Increased numbers of macrophages may be C. Myeloid-erythroid (M:E) ratio seen in immune-mediated disorders or with other 1. In general, M:E ratios are approximately causes of increased cell destruction 0.5:1 to 3:1 E. Cytochemistry and immunophenotyping are avail- 2. Decreased M:E ratio suggests increased RBC able for definitive identification of cell types production, decreased neutrophil production, or a combination Supplemental Reading 3. Increased M:E ratio suggests increased my- eloid cell production, decreased RBC produc- Thrall MA ed. Veterinary Hematology and Clinical tion, or a combination Chemistry. Philadelphia, 2004, Lippincott Williams & D. Maturation Wilkins. 1. Approximately 80% to 90% of the cells should be Villiers E, Blackwood L. BSAVA Manual of Canine and more mature cells (metamyelocytes, bands, neu- Feline Clinical Pathology. Gloucester, UK, 2005, BSAVA. trophils; rubricytes, metarubricytes) (Box 3-1) Willard MD, Tvedten H. Small Animal Clinical Diagnosis by 2. Disorderly maturation suggests leukemia, my- Laboratory Methods. St Louis, 2003, Saunders. eloid hyperplasia, immune-mediated hemolytic anemia, or marked inflammation