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Screening Laboratory Test
Results
in Inherited Defects in Blood Coagulation
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Screening Test Results*
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Defect
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Characteristics
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PTT long; PT normal
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Factor XII, high mol wt kininogen, prekallikrein
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Laboratory test abnormality without clinical bleeding; must be distinguished by specific assays from factor XI deficiency in which posttraumatic and perioperative bleeding may occur
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PTT long; PT normal
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Factor XI
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Autosomal recessive; increased frequency in Ashkenazic Jews; posttraumatic and perioperative bleeding; diagnosis by specific assay; therapy for bleeding is to keep factor XI level > 30% with fresh frozen plasma 5–20 mL/kg/day
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PTT long; PT normal
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Factor VIII or IX
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Factor VIII deficiency (hemophilia A); factor IX deficiency (hemophilia B); X-linked transmission; mild or severe bleeding, depending on factor VIII or IX level
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PTT normal; PT long
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Factor VII
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Autosomal recessive; rare; severe deficiency (< 2%) results in serious bleeding; levels > 5% result in mild or no bleeding; recombinant factor VIIa is the therapy of choice
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PTT long; PT long
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Factor X, V, or prothrombin
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Autosomal recessive; rare; bleeding may be mild to severe; diagnosed by specific assays; therapy for factor X or prothrombin deficiency is fresh frozen plasma or prothrombin complex concentrate for bleeding episodes; therapy for factor V deficiency is fresh frozen plasma with or without platelet concentrates (supply platelet factor V)
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In afibrinogenemia (fibrinogen < 10 mg/dL), no clotting in PTT or PT because machine endpoint not triggered
In hypofibrinogenemia (fibrinogen 70–100 mg/dL), PTT and PT often prolonged by several seconds, thrombin time long
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Fibrinogen
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Severe bleeding in afibrinogenemia (homozygous state); posttraumatic and perioperative bleeding in hypofibrinogenemia (heterozygous state); therapy is cryoprecipitate (5–10 bags, each containing about 250 mg fibrinogen)
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PTT and PT long; thrombin time long
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Dysfibrinogenemia
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Manifestations vary (no, or only mild, posttraumatic and perioperative bleeding, tendency for thrombosis, wound dehiscence); fibrinogen low by clotting assay but normal by immunologic assay
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PTT normal; PT normal; thrombin time normal
Clot dissolves in 5M urea
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Factor XIII
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Autosomal recessive; rare; poor wound healing; spontaneous abortions in women; severe bleeding with < 1% of normal level; therapy is fresh frozen plasma (1–2 units q 4–6 wk is effective because half-life of factor XIII is about 10 days)
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PTT and PT normal; clot lysis times in 5M urea or saline are accelerated
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α2-Antiplasmin deficiency
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Severe bleeding in homozygotes; heterozygotes may have posttraumatic and perioperative bleeding; confirmation of diagnosis requires specific assay
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*PT results are typically reported as INR.
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). Factor XI deficiency is uncommon in the general population but common in descendants of European Jews (gene frequency about 5 to 9%). Bleeding typically occurs after significant injuries, including trauma or surgery, in homozygotes or compound heterozygotes.
