complete blood count and anemia
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DESCRIPTIONComplete Blood Count and Anemia. Clinical Pathology. Blood Composition. Separates into three components: Red Blood Cells (RBC’s) White Blood Cells and platelets (buffy coat) Plasma Bottom 1/3 to ½ of tube contains the heaviest of cellular material (the RBC’s). - PowerPoint PPT Presentation
Complete Blood Count and AnemiaClinical Pathology
Blood CompositionSeparates into three components:Red Blood Cells (RBCs)White Blood Cells and platelets (buffy coat)Plasma
Bottom 1/3 to of tube contains the heaviest of cellular material (the RBCs).
Hematocrit=PCV (Packed Cell Volume)To determine hematocrit, whole blood is centrifuged to pellet the red blood cells.Plasma remains on the top of the red cells.The fraction of blood that is packed is the hematocrit and is read as a percentage.
Complete Blood CountProvides a minimum set of values and is cost effective.Can be done manually or with automated systems.CBC should contain:Packed Cell Volume (PCV or Hct)Plasma Protein ConcentrationTotal White Blood Cell countBlood smear with morphologyWBC differential countReticulocyte count
Manual ProceduresPCV- whole blood is collected in anticoagulant, placed in capillary tube, sealed, centrifuged and read.Total protein- plasma is read with a refractometer.
More Manual ProceduresAbsolute WBC: Total number of white blood cells in the blood. Unopette hematocytometer test kits are used to lyses RBCs and to make a 1:100 dilution.WBCs are counted within the grid and calculated to reflect the WBC in the blood.
Manual Procedures ContinuedDifferential Leukocyte Count: a relative count is performed by counting and classifying at least 100 leukoctyes. This gives a percentage of each cell type which is then used to calculate the absolute numbers of each cell type.May use a counter in order to perform this count.
InstrumentationElectronic cell counters: based on the principle that cells are poor electrical conductors. Measured volume of diluted blood is drawn between two electrodes, causing a resistance in the electrical current.QBC: Quantitative Buffy Coat SystemUtilizes differential centrifugation and quantification of cellular elements in a specialized microhematocrit tube.
Red Blood Cell IndicesPCV (hematocrit)Hemoglobin Concentration Total red blood cell count
These are used to classify the type of anemia.
AnemiaLiterally means no blood but clinically means low total blood hemoglobin.
Absolute anemia: most common, caused by failure to produce adequate numbers of cells or by a loss of cells at a rate greater than can be produced.
Clinical Signs of AnemiaPale mucous membranes Exercise intoleranceTachycardiaPantingIcterus if anemia is caused by RBC breakdown in bloodstream.
Classification of AnemiaBy RBC size (MCV):MacrocyticErythrocytes are larger than normal. Usually in the presence of regenerative anemia.May be seen in FeLvMay see anisocytosisNormocyticMicrocyticCells are smaller than normal which has been determined by Mean Cell Volume (MCV).Usually occurs with iron deficiency caused by chronic blood loss or parasitismBy Hemoglobin concentration (MCHC)HypochromaticRBCs have decreased density of the characteristic hemoglobin color.Frequently observed in iron deficiency caused by chronic blood loss or parasitism.Normochromatic
MCVDescribes cells as normocytic, microcytic, or macrocytic. Calculates the average volume of rbcs.
MCV=(Hematocrit x 10)/RBC count in millions
Ex:Canine patient with hematocrit of 42% and RBC count of 6 million/ul.
MCV causes of IncreasesReticulocytosisCongenital issues (poodles)Cats with FeLvRBC agglutinationB12 deficiency (rare)
MCV causes of decreasesAbnormal Hgb synthesis (iron deficiency from chronic blood loss is the most common).Immature animalsDogs with PSS.Congenital (Akitas)
MCHCMean Corpuscular Hemaglobin Concentration describes cells as normochromatic or hypochromatic.
MCHC= (Hgb)/(Hct) x 100
Ex.Same patient as before with Hgb content of 14 g/dL
MCHC causes if highIntravascular hemolysisInaccurate Hgb reading (Heinz bodies, lipemia, etc).Machine errorTrue hyperchromasia does not exist.
MCHC causes if lowSmall reticulocytesIron deficiency.
Classification According to Bone Marrow ResponseRegenerative anemia:Characterized by evidence of increased production and delivery of new erythrocytes into circulation.Usually suggests an extra bone marrow cause (blood loss, hemolysis, etc.).,Diagnosis:Peripheral blood smear.Will see macrocytosis, polychromasia with Wrights stain, reticulocytosis with methylene blue stain, may also see increased numbers of nucleated RBCs
Nonregenerative anemia:Indicates anemia is result of bone marrow defect.No response evident in peripheral blood.Marrow examination may be helpful with the diagnosis.
Reticulocyte CountProbably the most important diagnostic tool used in the evaluation of anemia.Expressed as a % of the RBCs present.Corrected to take in account the reduced number of circulating RBCs in the anemic animal.Called CRC or Corrected Reticulocyte CountThe lifespan of a normal RBC is about 100 days.Bone marrow should replace 1 % of the RBCs daily so the reticulocyte count should be 0.5-1.5%.
Reticulocyte count continuedExpressed as # of retics/100 RBCsSome species variation in reticulocyte response exists.Normal horse and cattle blood do not have reticulocytes.CRC= (patient Hct)/(Normal Hct) x reticulocyte count
ExampleDog with an observed reticulocyte count of 9 % and Hct of 25%. Normal Hct is 45.
Interpretation A (expressed in %):Normal Less than or equal to 1 in dogLess than or equal to 0.4 in catMildDog: 1-4Cat: 0.5-2ModerateDog: 5-10Cat: 2-3MarkedDog: greater than 10Cat: 3-4
Blood Loss AnemiaResults from excessive hemorrhage although source can be subtle.Must determine if blood loss is internal or external.Possible causes:TraumaPersistent bleeding lesions ThrombocytopeniaCoagulopathiesHeavy parasitismIatrogenic causes
Acute Blood LossAnemia due to loss of blood in a sudden episode.All RBC parameters are normal for the first 12 hours.Hypovolemic shock can be apparent prior to a decreased PCV.Anemia will be normocytic, normochromatic, and apparently unresponsive with a low CRC.By day 4-5, the retic count increases and the anemia appears responsive.
Chronic Blood LossBlood is lost slowly and continuously for a period of time.Body compensates for anemia by lowering oxygen-hemoglobin affinity, preferential shunting of blood to vital organs, increased cardiac output (tachycardia), and increased levels of erythropoietin.Anemia remains unresponsive unless iron stores are depleted.With decreasing iron stores, erythropoiesis is limited and RBCs become smaller and deficient in Hgb (microcytic and hypochromic).Clinical signs include lethargy, weakness, decrease exercise tolerance, anorexia, pallor, lack of grooming, mild systolic murmur.
Diagnostic TestsHemogram: may see increased WBC and platelets.Total protein: decreasedCoagulation testing: platelet count, PT, PTT, ACT.Fecal Float: Hookworms, WhipwormsFluids analysis from body cavities
Hemolytic AnemiasResult of increased erythrocyte destruction within the body.Intravascular hemolysis: desctruction of erythrocyctes within the blood vessels and loss of Hgb from the cells.Extravascular hemolysis: RBCs are lysed following phagocytosis.
DifferentialsImmune-mediated disease: AIHA, drug induced, neonatal isoerythrolysis.Parasitic: Ehrlychiosis, Babesiosis, Hemobartonellosis, Anaplasmosis.Toxic: Heinz body anemias, snake venom, bacterial toxins.Infectious: EIA, Leptospirosis, ClostridiaFragmentation: Splenic torsion, Splenic neoplasia, DIC