Partial Thromboplastin Time

Also written as PTT.

Prothrombin Time is normal, Activated partial thromboplastin time (APTT)

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Study material on Partial Thromboplastin Time

Practice questions on Partial Thromboplastin Time

A 20-year-old man presents with recurrent joint bleeds. His prothrombin time is normal, activated partial thromboplastin time (APTT) is prolonged, thrombin time (TT) is normal. Which coagulation factor abnormality is most likely?

Answer: C. An isolated prolonged APTT with normal PT and TT, plus haemarthroses, is classic for haemophilia A. ---

A 35-year-old man has no clinical evidence for bleeding and he feels fine. As part of a pre-operative workup for a hernia repair, laboratory studies show Hgb 14.8 g/dL, Hct 45%, MCV 96 fL, WBC count 8500/microliter, and platelet count 275,000/microliter. His prothrombin time is normal, but the partial thromboplastin time is prolonged. A deficiency of which of the following coagulation factors is m

Answer: D. An isolated prolonged PTT with a normal PT and no clinical bleeding history typically indicates a deficiency in a factor involved solely in the intrinsic pathway, such as Factor XII, prekallikrein, or high molecular weight kininogen. Factor XII deficiency is the most common of these and does not usually cause bleeding symptoms.

A 20-year-old man is actively bleeding from multiple sites during surgery. He has a CBC that shows a WBC count of 4500/microliter, Hgb 7.6 g/dL, Hct 23.9%, MCV 98 fL, and platelet count 75,000/microliter. His prothrombin time is 30 seconds and partial thromboplastin time 63 seconds. What is the best blood product to use for him in this situation?

Answer: B. The patient has anemia (low Hgb), thrombocytopenia (low platelets), and prolonged PT/PTT (coagulopathy). This indicates a need for both red blood cells to improve oxygen-carrying capacity (addressed by PRBCs) and coagulation factors to correct the bleeding diathesis (addressed by FFP, which contains all coagulation factors).

A 12-year-old boy has had multiple episodes of bleeding since infancy. It is characterized by hemarthroses and decreased joint mobility. His prothrombin time (PT) is normal, but the partial thromboplastin time (PTT) is elevated. When his plasma is mixed with normal plasma, the PTT is not elevated. His platelet count is normal. Which of the following is the most likely cause for his illness?

Answer: C. Hemarthroses (joint bleeding), normal PT, elevated PTT, normal platelet count, and correction of PTT upon mixing with normal plasma are classic findings of a congenital intrinsic pathway factor deficiency, most commonly Hemophilia A (Factor VIII deficiency) or Hemophilia B (Factor IX deficiency). Hemophilia A is the most common severe form.

A 35-year-old man has no clinical evidence for bleeding and he feels fine. As part of a pre-operative workup for a hernia repair, laboratory studies show Hgb 14.8 g/dL, Hct 45%, MCV 96 fL, and WBC count 8500/microliter, and platelet count 275,000/microliter. His prothrombin time is normal, but the partial thromboplastin time is prolonged. A deficiency of which of the following coagulation factors

Answer: B. A prolonged PTT with a normal PT suggests a defect in the intrinsic or common pathway of coagulation. Factor VIII deficiency (Hemophilia A) is a common inherited disorder that causes a prolonged PTT but a normal PT. Factors VII and X are involved in the extrinsic and common pathways, respectively, and would affect PT. Factor XIII is involved in clot stabilization.

A 20-year-old man is actively bleeding from multiple sites during surgery. He has a CBC that shows a WBC count of 4500/microliter, Hgb 7.6 g/dL, Hct 23.9%, MCV 98 fL, and platelet count 75,000/microliter. His prothrombin time is 30 seconds and partial thromboplastin time 63 seconds. What is the best blood product to use for him in this situation?

Answer: B. This patient has evidence of significant coagulopathy (prolonged PT and PTT) and potentially thrombocytopenia (platelet count 75,000/microliter, which is low in the context of active bleeding), along with anemia. Fresh frozen plasma (FFP) contains all clotting factors and is the best choice to rapidly correct coagulopathy. Packed red blood cells would address anemia, cryoprecipitate would provide fibrinogen and Facto

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