Platelet Estimation and Hematology Analyzers Flashcards
Platelets
Technical Name
Thrombocytes
Platelet Count vs Estimate
Count
* written out as a number (uL)
Estimate
* range of platelets per oil field
Platelet Counting
- 8-12 platelets / oil field
- 1 platelet/field = 15-20,000 /uL
- Describe as adequate, increased, or decreased
- Can’t detect abnormal morphology
Platelet Estimate
Increased or Decreased
- Record as decreased or increased
- State how many are seen (range) in field
- Look for clumps if decreased amounts
Thrombocytopenia
- Decreased platelet amounts
- Most common coagulation disorder in small animals
- Cause often unknown
Thrombocytopenia
Indications
- Immune-mediated disease
- Bone marrow dysfunction
- Splenic dysfunction
- DIC
Giant Platelets
- Approaching size of RBC
- Indicative of early bone marrow release
- Normal in cats and cavaliers
Platelet Clumps
- Seen especially at feathered edge
- Most common in cats
- Note in place of adequate/decreased
Normal Platelet Count
Dogs vs Cat
Dog
* 200,000 - 500,000 /uL
* average 300,000
Cat
* 300,000 - 700,000 /uL
* average 450,000
Coagulation Stages
- Mechanical Phase
- Chemical Phase
- Final Phase
Mechanical Phase
Coagulation
- Primary hemostasis
- Initiated when vessel torn or ruptured
- Formation of platelet plug
- Von Willebrand factor stabilizes plug
Chemical Phase
Coagulation
- Secondary hemostasis
- Formation of clot via coagulation cascade
Coagulation Cascade
Multiple coagulation factors that each experience chemical reactions to initiate next step of pathway
* Extrinsic
* Intrinsic
* Common
Final Phase
Coagulation
Breakdown of fibrin clot
Common Pathway
Coagulation Cascade
Forms final clot
Calcium and Platelets
- Platelets release calcium
- Calcium important for all stages of coagulation cascade
- EDTA helps bind calcium to prevent clotting
Platelet Formation Stages
- Myeloid Stem Cells
- Megakaryoblasts
- Promegakaryocyte
- Megakaryocytes
- Thrombocytes
Platelets
- Non-nucleated fragments of cytoplasm
- Multiple, fine pink-purple granules
Thrombocytosis
Increase in platelet numbers
Thrombocytopathia
Abnormal platelet function
Thrombocytopathia Causes
- Drugs - NSAIDS, heparin
- Liver, renal, or pancreatic disease
- Vascular disorder
- Hyperadrenocorticism (cushings)
Platelet Approximation
- Average # of PLTs per 10 fields
- Multiply by 15,000 or 20,000
- Record as whole number /uL
Reticulated Platelets
- Newly released platelets
- High level of RNA
- Need special stain
- Indicates bone marrow responsiveness
BMBT
- Buccal Mucosa Bleeding Time
- Primary test for detecting thrombopathia
- Normal: 1-5 minutes
BMBT Test Setup
- Patient in lateral
- Expose mucosa
- Incision with lancet around premolars
- Wick away blood with paper
- Do every 5 seconds until bleeding stops
Abnormal BMBT Causes
- Thrombocytopenia - do PLT count first
- PLT dysfunction test
- Von Willebrand factor deficiencies -especially if normal PLT count
Coagulation Cascade Testing
- ACT
- APTT
- PT
- FDP and D-dimer
Activated Clotting Time
ACT
Evaluates for significant clotting factors
* intrinsic and common
ACT Testing
- Tube with diatomaceous earth or kaolin
- Preheat tube to 37 C
- 2 mL of blood
- Timer starts when blood enters tube
- Mix and place back into 37 C
- Check after 60 seconds, then every 5 for clots
ACT Normal
- Dog: 60-100 seconds
- Cat: 65-70 seconds
Abnormal ACT Causes
- Thrombocytopenia
- Abnormal intrinsic pathway
Activated Partial Thromboplastin Time
APTT
- Evaluates intrinsic and common pathways
- More sensitive than ACT
- Run on machine
APTT Testing
- Citrated plasma tube
- Centrifuge and remove plasma
- Place in plastic tube and freeze
Prolonged APTT Causes
- Acquired and hereditary disorders
- Heparin administration
Prothrombin Time
PT
- Evaluates extrinsic and common pathways
PT Testing
- Citrated plasma + thromboplastin reagent + another reagent
- Centrifuge and remove plasma
- Place in plastic tube and freeze
PT Normal
7-10 Seconds
Prolonged PT Causes
- Severe liver disease
- DIC
- Hereditary or acquired deficiencies
- Vitamin K deficiency
Vitamin K Deficiency
- PT time increased, followed by APTT and ACT
- PIVKA test early
- Treat with Vitamin K for several weeks
PIVKA Test
Differentiate rodenticide toxicity from primary hemophilia when ACT is prolonged
* slightly more sensitive than PT
PIVKA
Stands For
- Proteins that are
- Induced due to
- Vitamin
- K
- Absence
von Willebrand Disease
- Most common inherited coagulation disorder in domestic animals
- Deficient production of vWF - assists in PLT aggregation
- See with dobermans
D-Dimer and FDP Test
- Evaluates tertiary hemostasis (fibrinolysis)
- Identifies DIC
FDP
Fibrin/Fibrinogen Degradation Products
* evaluates fibrinolysis
* Less sensitive than D-Dimer tests
* Created prior to fibrin clot formation
D-Dimer
- More sensitive than FDP tests
- Only made when fibrin clot has formed
Hemophilia A
Most common inherited coagulation factor disorder in dogs
Liver and Coagulation
Liver is primary place for coagulation factor production
DIC Test Results
- Prolonged APTT, PT, and thrombocytopenia
- Increased FDP and D-dimers
