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Case Questions and Answers

 

by Dr. Marjory Brooks

Case 1 & 2 Questions:

  1. What is your initial differential diagnosis?  
    Case 1 Answer  |   Case 2 Answer

  2. What additional coagulation tests could be performed to make a definitive diagnosis?  
    Case 1 Answer  |   Case 2 Answer
    – see coagulation pathways diagram and diagnostic algorithm to help formulate your diagnostic plan

  3. What sample-type is required for this coagulation testing?  
    Case 1 Answer  |   Case 2 Answer
    – see the coagulation lab sampling page for detailed instructions

  4. Based on coagulation test results how would you treat this patient?  
    Case 1 Answer  |   Case 2 Answer

  5. How would you counsel this owner?  
    Case 1 Answer  |   Case 2 Answer

 

Case 1. Coagulation test results:

APTT = 25.4 (reference range = 14.5 to 19.0 seconds)
PT = 31.0 (reference range = 15.0 to 20.0 seconds)
TCT = 5.0 (reference range = 5.0 to 8.0 seconds)
Fibrinogen = 150 (reference range = 76 to 270 mg/dL)
Factor VII activity = 6% (reference range > 50%)
Factor VIII activity = 100% (reference range > 50%)
Factor IX activity = 20% (reference range > 50%)
Factor X activity = 7% (reference range > 50%)


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Case 2. Coagulation test results:

APTT = 115.0 (reference range = 14.5 to 19.0 seconds)
PT = 18.5 (reference range = 15.0 to 20.0 seconds)
TCT = 6.5 (reference range = 5.0 to 8.0 seconds)
Fibrinogen = 112 (reference range = 76 to 270 mg/dL)
Factor VIII activity = 100% (reference range > 50%)
Factor IX activity = 85% (reference range > 50%)
Factor XI activity = 95% (reference range > 50%)
Factor XII activity = 2% (reference range > 50%)

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Coagulation Pathways and Coagulation Screening Tests

Coagulation Pathways Diagram
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Diagnostic Algorithms Based on Coagulation Screening Tests

Coagulation Algorithms Diagram
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Case 1 Answers:

  1. What is your initial differential diagnosis?
    Prolongation of both the APTT and PT screening tests indicates deficiencies of both intrinsic and extrinsic pathways and/or severe fibrinogen deficiency.
  2. What additional coagulation tests could be performed to make a definitive diagnosis?
    Specific measurement of fibrinogen or the thrombin clotting time (TCT) screening test will rule out fibrinogen deficiency as the cause of prolonged APTT and PT. For patients with normal fibrinogen, measuring Factor VII and other vitamin K-dependent factors (Factors II, IX, X) will confirm or rule out a vitamin K-dependent coagulopathy. If all of these factors are normal, then Factor V assays could be performed.
  3. What sample-type is required for this coagulation testing?
    Citrate plasma (plasma from a blue top tube) is the only valid sample for coagulation factor assays.
  4. Based on coagulation test results, how would you treat this patient?
    The pattern of coagulation abnormalities for this patient is diagnostic for a vitamin K-dependent coagulopathy. Supplementation with vitamin K1 at an initial dose of 1 mg/lb/day (0.5 mg/kg/day) is indicated and should reverse coagulopathy within 24 to 48 hours of treatment. See vitamin K therapy page for more information.
  5. How would you counsel this owner?
    Anticoagulant rodenticide is the most common cause of severe vitamin K deficiency in dogs and cats. The owner should check to ensure that this cat has no access to bait stations, or chance of secondary poisoning by ingestion of poisoned prey. Devon Rex cats have a rare hereditary coagulopathy caused by abnormal vitamin K metabolism. This differential should be considered based on breed and family history and all available relatives should be screened to identify any other affected individuals and likely carriers. Affected cats with signs of bleeding can be treated with vitamin K1 and can undergo surgery with pre-and post-operative vitamin K1 therapy.

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Case 2 Answers:

  1. What is your initial differential diagnosis?
    Specific prolongation of the APTT screening test indicates deficiency of an intrinsic or contact pathway coagulation factor.
  2. What additional coagulation tests could be performed to make a definitive diagnosis?
    Specific measurement of the intrinsic factors (Factors VIII, IX, XI) and Factor XII will define the cause of long APTT. Ruling out Factor VIII or IX deficiency (hemophilia A or B) is important because they are severe congenital bleeding disorders that appear through spontaneous mutation and are not restricted to a single breed or inbred lines.
  3. What sample-type is required for this coagulation testing?
    Citrate plasma (plasma from a blue top tube) is the only valid sample for coagulation factor assays.
  4. Based on coagulation test results, how would you treat this patient?
    Unlike hemophilia A or B, cats with Factor XII deficiency do not express a bleeding tendency. They do not require transfusion for surgery and do not require any special medical management for invasive procedures.
  5. How would you counsel this owner?
    Factor XII deficiency is a common finding in cats. While Factor XII deficiency delays clotting time in the APTT screening test, it is not a risk factor for abnormal bleeding and has no apparent deleterious effects. Factor XII deficient cats require no special treatment and should enjoy normal life span.

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