Ch. 26 Coagulation

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Ch. 26 Coagulation
2013-02-14 23:19:36
Coagulation Test Procedure

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  1. PT (10-13 seconds)
    Prothrombin Time
    Measures the time required to form a fibrin clot after activation of the Extrinsic pathway
  2. PTT (20-35 seconds)
    Partial Thromboplastin Time
    • Heparin
    • Measures the time required to form a fibrin clot after activation of the Intrinsic Pathway
  3. Fibrinogen (200-400 mg/dl)
    • If low fibrinogen, time will be high.
    • If high fibrinogen, time will be low.
    • The time required for the clot to form is inversely proportional to the fibrinogen concentration.
  4. (FDP)
    Fibrin Degradation Products
    • Fibrinolytic activity of plasma breaks fibrinogen and fibrin into smaller fragments called fibrin degradation products (Fibrin split products)
    • When patient serum containing FDPs is added to latex particles coated with antibodies, these antibodies cross react with the FDPs to produce visible agglutination.
    • Positive FDPs are associated with increased fibrinolysis (DIC, PE, DVT)
    • FDP does not differentiate between primary fibrinolysis and Secondary because it uses an anti-fibrinogen antibody that reacts with FDPs and fibrinogen.
  5. D-Dimer
    • Specific type (FDP)
    • Plasmin degrades fibrin into smaller D,E,X,Y fragments.
    • More specific for Secondary fibrinolysis becaust the D-dimer is formed from the degradation of cross-linked fibrin.
    • Useful to diagnose DIC associated with 20
    • D-dimer latex particles coated with anti-d dimer antibody
  6. Mixing Studies (PT/PTT)
    Factor Deficiency
    Results return/approach the normal range

    The normal plasma will "correct" the patient plasma and the PT/PTT test will return to within the normal range.
  7. Inhibitor
    Results do not approach the normal range
  8. Elevated PT/PTT test can be caused by:
    • A factor deficiency or a circulating anticoagulant (antibody directed against a coagulation factor also known as an inhibitor)
    • Differentiate between these two, the abnormal patient plasma is mixed with an equal volume of normal plasma and the PT and/or PTT test is repeated with the patient plasma-normal plasma mixture.
  9. Circulating anticoagulant
    The normal plasma is also inhibited and the PT/PTT test will remain elevated
  10. Substitution Studies
    • Screening tests such as the PT and PTT are increased, it is often necessary to ID the specific factor deficiency
    • Different types of plasma or serum can be added to patient plasma to test for a correction of the PT or PTT tests
  11. Adsorbed plasma
    1,5, 8, 11,12

    • Plasma mixed with barium sulfate or aluminum hydroxide and centrifuged
    • Group II removed
  12. Aged serum

    Incubate serum @37C for 24 hours 1,2,5,8 removed.
  13. PFA-100
    Replaced bleeding time
    • Sodium citrate whole blood aspirated through a small tube.
    • DO NOT centrifuge prior to testing
    • 2 types of apertures used (Collagen and Epinephrine; Collagen and ADP)

    • Platelet activation and aggregation will clog the aperature and stop the flow of blood.
    • Time required to stop blood flow is the closure time (reflects qualitative plt. function)
  14. PFA-100 continue
    If the CEPI is elevated then CADP is performed
  15. Causes of elevated closure time
    • Aspirin
    • Platelet counts <100,000
    • HCT < 30%
    • Lipemia
    • Uremia (renal failure)
  16. CEPI:
    80-150 seconds
  17. CADP
    60-100 seconds
  18. Bleeding time test isn't performed anymore because:
    • Operator dependancy
    • Scarring
    • Insensitivity to some plt. disorder
    • Poor indicator of surgical bleeding
  19. Factor Assay 50-150%
    (V, VII, VIII, IX, XI)
    • Specific factor assays can determine the activity of specific coagulation proteins.
    • Activity expressed as a % of normal
    • Patient plasma is mixed with a known factor deficient plasma
    • It's ability (or inability) to correct a known factor deficiency plasma determines how much of the factor the patient possesses.

    Correct=Normal PTT or PT result
  20. Bleeding Time Test (IVY)
    Measurement of platelet function
    As the cut injures the sub-endothelial lining of the capillaries, platelets adhere and aggregate at the injury, forming a platelet plug stopping the bleeding
  21. Bleeding Time increased in:
    • vWD
    • Bernard-Soulier Syndrome
    • Glanzmann's thrombosthenia
    • Platelet storage pool disease
    • Aspirin ingestion
    • Decreased platelet count <100,000
    • Severely decreased fibrinogen concentrations
  22. Clot Retraction
    red tube
    • Function of platelet function and the platelet count.
    • If platelet decreased in number or function clot retraction is decreased.
    • Increased fibrinolysis will also decrease clot retraction because the clot is dissolved as fast as retraction can occur.
    • Normal clot retraction begins within 1 hour and complete by 24 hours

    Normal: 45-65%
  23. Thrombin Time
    < 20 seconds
    • Converts fibrinogen to fibrin monomers and into fibrin
    • Time required for clot formation increased by:   Decreased Fibrinogen concentration, Inhibitors (antibodies), Increased immunoglobulin concentrations, Heparin, FDP