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Zorluk: ZorInterpreting Laboratory Results

A hospital's clinical laboratory frequently receives requests to evaluate complex hematologic and coagulation abnormalities in acutely ill patients. Review the following laboratory profiles and match each diagnostic entity with its characteristic hematologic laboratory pattern.

Reference Ranges:
ParameterReference Range
Prothrombin time (PT)11-14 seconds
Activated partial thromboplastin time (aPTT)25-35 seconds
Platelet count150,000-400,000/μL
Fibrinogen200-400 mg/dL

Identify the correct laboratory pattern for each diagnostic entity.

  • Disseminated intravascular coagulation (DIC)PT is 24 seconds, aPTT is 62 seconds, platelets are 42,000/μL, and fibrinogen is 75 mg/dL. Peripheral blood smear shows abundant schistocytes.
  • Thrombotic thrombocytopenic purpura (TTP)PT is 12 seconds, aPTT is 30 seconds, platelets are 16,000/μL, and fibrinogen is 350 mg/dL. Peripheral blood smear shows schistocytes with elevated lactate dehydrogenase.
  • Lupus anticoagulant effectPT is 13 seconds, aPTT is 85 seconds, and platelets are 210,000/μL. A 1:1 mixing study with normal plasma yields an aPTT of 81 seconds.
  • Intrinsic pathway factor deficiency (e.g., Factor VIII)PT is 12 seconds, aPTT is 72 seconds, and platelets are 245,000/μL. A 1:1 mixing study with normal plasma yields an aPTT of 32 seconds.
  • Severe vitamin K deficiencyPT is 32 seconds, aPTT is 60 seconds, platelets are 310,000/μL, and fibrinogen is 320 mg/dL. A 1:1 mixing study corrects both the PT and aPTT to normal reference values.

Cevap

DIC matches the profile showing consumptive coagulopathy (prolonged PT/aPTT, low platelets, low fibrinogen). TTP matches the profile showing isolated thrombocytopenia with normal coagulation times. Lupus anticoagulant matches the isolated prolonged aPTT that fails to correct on a mixing study. Factor VIII deficiency matches the prolonged aPTT that completely corrects. Vitamin K deficiency matches the prolonged PT and aPTT that correct with a mixing study, alongside normal platelets.
Accurate interpretation of these lab profiles requires synthesizing platelet counts, fibrinogen levels, PT, aPTT, and the response to mixing studies. Consumptive processes (DIC) deplete platelets, fibrinogen, and coagulation factors. Primary platelet aggregation disorders (TTP) spare coagulation factors. Deficiencies (Factor VIII, Vitamin K) correct when mixed with normal plasma, whereas inhibitors (Lupus anticoagulant) do not correct.

Adım Adım Çözüm

1
Differentiate consumptive vs. non-consumptive microangiopathic hemolytic anemias.
DIC shows profound coagulation factor consumption (low fibrinogen, prolonged PT/aPTT), whereas TTP features severe thrombocytopenia and schistocytes with completely normal PT, aPTT, and fibrinogen.
This isolates the diagnoses of DIC and TTP based on the status of the secondary hemostatic cascade.
2
Analyze the isolated aPTT prolongations using the results of the 1:1 mixing studies.
The profile with an isolated prolonged aPTT that corrects upon mixing represents an intrinsic factor deficiency. The profile with an isolated prolonged aPTT that fails to correct represents an acquired inhibitor, specifically the lupus anticoagulant effect.
Mixing studies distinguish between a lack of clotting factors (which normal plasma replenishes) and the presence of an autoantibody inhibitor (which acts against the factors in the normal plasma).
3
Evaluate the profile with combined prolongation of PT and aPTT but normal platelets and fibrinogen.
This profile corrects with a mixing study, confirming a multiple-factor deficiency state. It aligns perfectly with severe Vitamin K deficiency affecting factors II, VII, IX, and X.
Unlike DIC, Vitamin K deficiency does not consume platelets or fibrinogen, allowing for precise differentiation of generalized bleeding disorders.

Anahtar Kavram

Interpretation of Coagulation Profiles and Mixing Studies
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Interpreting Laboratory Results

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