Equine Hematology Flashcards
Obj: Identify when various assays are commonly used in practice
Obj: Recognize why certain tests are useful
Obj: Improve familiarity of what laboratory assays are used for equine patients
What is the function of Albumin? ref. interval for horses?
- 3.0-4.1 g/dL
- Major protein responsible for maintaining oncotic pressure
- Important for binding and transport
- other proteins, drugs, hormones
What is Hypoalbuminemia? etiologies?
- Decreased synthesis or increased loss
- Etiologies
- Hepatic failure - end-stage in horses
- albumin has ~19 day half-life
- Glomerulonephritis: rule out with UA
- Protein losing enteropathy
- Infectious - Salmonella spp, Clostridium spp
- Inflammatory - NSAID toxicosis, cantharidin toxicity
- Hepatic failure - end-stage in horses
- Decreased Albumin is consistent with DIC or end stage liver failure
What is Hyperalbuminemia?
- Increased albumin
- consistent with dehydration
What are Globulins? functions? Ref intervals for horses?
- 2.6-4.0 g/dL
- Composed of alpha, beta and gamma globulin fractions
- Fibrinogen, Transferrin, immunoglobulins
- Lipoproteins and acute phase proteins migrate as alpha and beta (fibrinogen) globulins
- Increased w/ tissue injury
- Acute inflammation
- Complement and iron-containing proteins (transferrin a negative acute phase protein) migrate as beta globulins
What causes increases in globulins?
- Monoclonal gammopathies (represent by a spike in the gamma fraction) are observed w/ multiple myeloma and some lymphomas
- Lipoproteins and acute phase proteins (migrate as alpha and beta globulins) increase with tissue injury or acute inflammation
- Increased beta fraction may be observed with intense immune response (complement system)
- Increased Fibrinogen is consistent with inflammation
- good correlation with disease severity
- may not peak for ~48hrs after insult
What is Fibrinogen? Ref. Interval?
- 100-400 mg/dL
- a β-globulin and is classified as an acute phase protein associated with coagulation and inflammation
- values may not peak for approximately 48hr
- Important to evaluate in sick neonatal foals - aids in establishing in utero infection
- Increased values correlate with disease severity
What is polyclonal gammopathy? etiologies?
- overproduction of more than one class of immunoglobulins (antibodies) by plasma cells
- Etiologies:
- chronic inflammation
- Immune mediated disease
- lymphoid neoplasms
- multiple myeloma or lymphoid neoplasms
What is Total serum protein? Ref interval for horses?
- 5.6-7.6 g/dL
- Contains - Albumin and Globulins
What causes an increase in total serum proteins?
- Dehydration
- Inflammation
- Multiple Myeloma
- Sepsis
- Non-septic inflammation or Myeloma
What causes a decrease in Total Serum Proteins?
- Failure of Passive Transfer in foals
- Decrease is due to loss as a result of renal or GIT disease
- Reduced production may result from starvation or end-stage liver disease
What is Alkaline Phosphatase? reference intervals in horses
- 75-220 U/L
- ALP isoenzymes are present in all tissues
- ALP activity in healthy horses is due to hepatic origin
- ALP is bound to intracellular microsomal enzymes
- Placental ALP might be found in serum from pregnant mares
What causes an increase in ALP?
- Increases w/ cholestasis, pregnancy, and bone growth
- Cholestasis causes induction of hepatic ALP w/ increased serum activity
- Usually normal or mildly increased w/ acute hepatitis
- AST might increase significantly
- Increased ALP is common in healthy young growing foals
What is Alanine aminotransferase (ALT)? ref. interval in horses?
- Very low in horses
- NOT useful in detecting liver disease
What is Aspartate aminotransferase (AST)? Ref. interval?
- 160-412 U/L
- Present in most cells
- Used as a diagnostic enzyme for liver or muscle disease because of its particularly high levels in these tissues
- Plasma half-life is longer ~18hrs
What causes an increase in AST?
- Sublethal injury and necrosis in muscle and hepatocellular permeability
- Might occur for up to 14 days following muscle or liver injury
- Increased AST & CK = muscle damage
- Increased AST & SDH = hepatic damage
What is Creatine Kinase (CK)? Ref. Interval?
- 60-330 U/L
- isoenzymes are present in skeletal (CKMM) and cardiac (CKMB) and brain (CKBB)
- important to differentiate cardiac disease
What causes an increase in CK?
- Muscle necrosis
- atrophy, neoplasia, or ischemic injury w/out degeneration or necrosis will NOT increase serum levels
- Secondary to vascular impairment (vasculitis or shock)
- Minimal increase (500-1000 U/L) w/ IM injections, laying down excessively (colic)
- Mild to moderate (<2000 U/L) increase may indicate poor muscle tolerance for exercise such as subclinical exertional rhabdomyolysis or with equine motor neuron disease
- Significant increase (>2000 U/L) with exertional rhabdomyolysis
What is Gamma-glutamyltransferase (GGT)? ref. interval?
- 6-32 U/L
- Associated with microsomal enzymes and cellular cytosol
- Greatest activity in canalicular surfaces of hepatocytes, bile duct epithelium, and renal convoluted tubules
What causes increases in GGT?
- Increases w/ cholestasis
- Secondary to hepatocellular damage
- Mild increases might be seen with obstructive colonic disease (ascending hepatitis)
- Increased urine GGT-creatinine ratios (>25:1) - Acute Renal Failure
What is Sorbitol Dehydrongenase (SDH)? Ref. Interval?
- 1-8 U/L
- high activity in hepatocellular cytosol
- Very short half-life (hrs) so continued increases are consistent w/ ongoing damage
What causes increases in SDH?
- Increase indicates acute change in hepatocellular permeability typically associated w/ hepatic injury or necrosis
- Obstructive GIT lesions (strangulating)
- Acute enterocolitis
- Mild increases may be associated with anoxia or shock
What is an Anion gap? Ref. Interval?
- 0 - 9
- Calculated value of all unmeasured serum cations minus all unmeasured serum anions:
- AG = [Na+ + K+] - [Cl- + HCO3-]
- Most changes are a result of unmeasured anions such as small organic ions, albumin, and exogenous toxins
What causes an increase to the Anion Gap?
- Increases with metabolic acidosis
- lactic acidosis
- renal insufficiency
What causes a decrease in Anion Gap
- Rare
- Hemodilution
- hypoalbuminemia
What are Bile Acids (BA)? Ref Interval?
- 0 - 20 μmol/L
- The final product of cholesterol metabolism
- Bile acids are produced in the liver, released into the GIT lumen and resorbed in the ileum and return to the liver via portal circulation
- measured in combo with bilirubin concentration and serum (liver) enzyme activities
What affect does fasting have on Bile Acids?
- < 20 μmol/L
What What causes an increase in Bile acids?
- Hepatopathies associated with reduced hepatic function
What is Bilirubin? Ref Interval?
- total 0.0 - 3.2 mg/dL
- direct 0.0 - 0.4 mg/dL
- The product of hemoglobin metabolism resulting from processing of senescent RBCs and nonheme porphyrins
What are the causes of hyperbilirubinemia?
- Most commonly predominantly indirect bilirubin (unconjugated)
- Anorexia - reduced ligandin
What Calcium is measured? Ref. Interval?
- 10.2 - 13.4 mg/dL
- Present in the serum in 3 forms:
- protein-bound ~50%
- complexed calcium
- ionized calcium
- Reported as total calcium
What influences the level of calcium in circulation? how
- Diet
- Calcitonin is produced in response to hypercalcemia and regulates PTH resorptive capacity on bone
- Vitamin D promotes calcium resorption by the intestinal mucosa
- Albumin
- Endogenous Hormones
- Parathyroid Hormone (PTH)
- promote renal tubular reabsorption and intestinal absorption of dietary calcium
- Parathyroid Hormone (PTH)
What causes Hypercalcemia?
- Hyperparathyroidism
- neoplasia
- gastric squamous cell carcinoma
- malignant lymphoma
- Hypervitaminosis D (plant toxicity)
- Excess dietary intake
- chronic renal failure
- maximal exercise
What causes Hypocalcemia
- Hypoalbuminemia
- Cantharidin toxicity
- lactation tetany
- transport tetany
- acute renal failure
- reduced intake
- GIT disease
- excess sweating
What is Chloride? Ref. Interval?
- 98 - 109 mEq/L
- Major extracellular anion
- changes in serum concentration may parallel changes in sodium and vary inversely with bicarbonate concentration
What causes Hypochloremia?
- Most commonly observed in association with loss due to upper GIT or large intestinal disease
- Esophageal obstruction
- anterior enteritis
- mechanical obstruction of small intestine
- colitis
What causes hyperchloremia?
- uncommon
- renal tubular disease
- renal tubular acidosis
What is creatinine? Ref. Interval?
- 0.4 - 2.2 mg/dL
- Nonprotein nitrogenous substance that originated endogenously from muscle metabolism
- Excreted by glomerular filtration
What causes an increase in serum creatinine
- reduced renal blood flow (GFR)
- Prerenal renal, or postrenal azotemia
- Well muscled horses (Quarter, Stallions, Draft breeds) have higher creatinine naturally
Why would creatinine be low/at the lower end of the reference range?
- Foals and older thin horses naturally
What is Glucose influenced by? Ref. Interval?
- 62 - 120 mg/dL
- Influenced by:
- diet
- insulin/glucagon
What causes hyperglycemia?
- Pituitary adenoma** in geriatric horses
- postprandially (eating)
- Catecholamine/glucocorticoid release:
- pain
- fear
- CNS disease
- stress
What causes hypoglycemia in horses?
- Adrenocortical insufficiency
- liver failure
- exertional extreme
- sepsis
- starvation
- malabsorption
- Artifactual w/ improper sample handling
- in vitro glycolysis by erythrocytes
What is the function of Magnesium? Ref Interval?
- 1.4 - 2.3 mg/dL
- diet dependent
- Cofactor for many enzyme reactions
- Balance maintained by intestinal absorption, renal excretion, lactation
What causes Hypomagnesemia in horses?
- Hypoaldosteronemia
- intestinal disease
- excess sweating
- cantharidin toxicity
What cases hypermagnesemia in horses?
- renal failure
- maximal exercise
How is Potassium measured in the body? Ref. Interval?
- ICF potassium is > than ECF potassium
- Serum measurements are not an accurate method of measuring whole body stores since cellular shifts frequently occur
- total body potassium concentration estimates must be made w/ respect to blood pH and disease processes
What causes Hypokalemia in horses?
- whole body depletion of body stores
- Redistribution into ICF
- Alkalemia
- anorexia
- GIT loss
- excess sweating
- urinary loss
What causes hyperkalemia?
- Academia
- maximal exercise
- tissue necrosis
- insulin deficiency
- oliguria
- uroperitoneum
- adrenal insufficiency
- hereditary hyperkalemic periodic paralysis of Quarter Horses
What causes false hyperkalemia?
- poor sample handling
- in vitro erythrocyte destruction results in release of intracellular stores
Where is sodium stored in the body? Ref Interval?
- 128 - 142 mEq/L
- most in the ECF
- remainder bound to skeletal bone
- Balance controlled by changes in water balance and aldosterone
- aldosterone increases sodium resorption in the kidney
What causes hyponatremia?
- Diarrhea
- excessive sweat loss
- adrenal insufficiency
- sequestration of fluid
- renal disease
What causes Hyponatremia with hyperkalemia?
- uroperitoneum
- adrenal insufficiency
What causes hypernatremia
- Dehydration
- salt poisoning
What is Total CO2? Ref Interval?
- 22 - 33 mEq/L
- HCO3 is major component
- changes in tCO2 are seen as changes in HCO3
What does decreased tCO2 indicate
metabolic acidosis (e.g diarrhea)
What does increased tCO2 Indicate?
alkalemia (e.g. esophageal obstruction)
What is Urea Nitrogen? Ref Interval?
- 11 - 27 mg/dl
- Produced from ammonia and excreted by glomerular filtration
- increased nitrogenous waste in circulation = Azotemia
What does increased Urea Nitrogen indicate?
- Prerenal, renal, or post renal disease
- protein catabolism
What causes Prerenal Azotemia?
- decreased renal blood flow without a functional change of the kidney
- Signs:
- Concentrated urine (S.G > 1.020)
- Urine osmolality 3x greater than serum osmolality
- no evidence of enzymuria
- low urine sodium concentrations
Why does Postrenal azotemia occur?
- Obstruction to urine outflow
- Ruptured bladder
Why would serum Urea Nitrogen be decreased?
- Low protein diet
- liver failure
- anabolic steroids
What is the reference interval of of WBC in horses?
5.6 - 12.1 x 103 /μL
What cells are part of the WBC count?
- Neutrophils
- lymphocytes
- eosinophils
- monocytes
- basophils
When are Basophils seen? Ref. Intervals?
- 0 - 0.3 x 103 / μL
- Uncommonly observed in the periphery (horses)
- Mya be observed in association w/ allergic dermatitis
What are eosinophils? when are they seen? Ref interval
- 0 - 0.78 x 103 /μL
- may increase with parasitic disease and allergic responses
- Intestinal parasitism and VLM rarely result in eosinophilia
- Eosinophilic granulocytic leukemia rarely reported
When is eosinopenia seen in horses?
hard to evaluate since horses have so few eosinophils in circulation
When is lymphocytosis/lymphopenia seen in horses? Normal ref interval?
- 1.16 - 5.1 x 103 / μL
- Lymphocytosis - excitement or exercise in young horses
- Lymphopenia -
- stress
- exogenous corticosteroids
- endotoxemia
- bacterial sepsis
- viral disease
- immunodeficiency
When is monocytosis seen? Normal ref. Interval?
- 0 - 0.7 x 103 / μL
- Monocytosis - consistent w/ chronic suppurative and granulomatous inflammation
What is the normal reference interval for neutrophils in horses?
- 2.9 - 8.5 x 103 /μL
When does neutrophilia occur in horses?
- Endogenous Catecholamine release → circulating neutrophilia due to release of the marginated pool
- stress
- excitement
- exercise
- Corticosteroids (endogenous or exogenous)
- release of marginated pool
- Acute bacterial infection
- chronic localized bacterial infections - rarely cause mild neutrophilia
- neoplasia
- tissue destruction
- Recovery form Endotoxemia - transient neutrophilia
What causes Neutropenia in horses? how?
- Bacterial sepsis
- neutrophils leave circulating pool → marginate to vascular endothelium
- Endotoxemia
- neutrophils leave circulating pool → marginate to vascular endothelium
- commonly causes ⇡ in band neutrophils in circulation
- Severe Inflammatory Disease
- neutrophils leave circulation to site of infection
- Bone Marrow dysfunction / Neoplasia
- rare
What toxic changes are seen neutrophils of horses with endotoxemia?
- cytoplasmic vacuolation
- basophilia
- Dohle bodies
- toxic granulation
What causes erythrocytopenia in horses?
- blood loss
- hemolysis
- parasitism
- renal failure
- chronic inflammation
- rarely hematopoietic malignancies
What is Polycythemia? causes?
- increased concentration of erythrocytes in blood
- “erythrocytosis”
- Causes:
- Dehydration
- splenic contraction
- high altitude
- chronic pulmonary disease / heart defects
- hepatocellular carcinoma
What erythrocyte abnormalities occur in horses?
- Erythrocytes are retained in the bone marrow until hemoglobin synthesis is complete
- polychromasia, and macrocytosis are rare
- Howell-Jolly bodies
- do NOT represent immature release
- Rouleaux formation - common
Ref Interval for erythrocytes in horses?
- 6 - 10.43 x 106 / μL
- HCT 32 - 43%
What are Reticulocytes? ref range?
- Ref Interval: 0
- Immature RBC’s
- not common in horses are reticulocytes stay in bone marrow until mature
What is the Ref Interval for Thrombocytes in horses? Reasons for Thrombocytopenia? Thrombocytosis?
- 117 - 256 x103 /μL
- Thrombocytopenia:
- DIC
- IMT
- Endotoxemia
- EIA
- Equine Ehrlichiosis
- LSA
- Pseudothrombocytopenia
- Clumping in EDTA
- Use of citrate or heparin
- Thrombocytosis:
- Chronic inflammation
- Rhodococcus equi
