Causes of Abnormal PT and/or aPTT

Prolonged Prothrombin Time (PT)

1. Acquired deficiency of FVII

     a. Early warfarin therapy

     b. Early vitamin K deficiency

     c. Early liver disease

2. Drugs

     a. Direct Xa inhibitors - Rivaroxaban, apixaban, edoxaban (typically prolong aPTT)

3. Congenital deficiency of FVII

4. Specific inhibitors to FVII (exceptionally rare)

Prolonged Activated Partial Thromboplastin Time (aPTT)

1. Therapeutic unfractionated heparin - Other anticoagulants may prolong the aPTT alone but typically prolong PT too

2. Nonspecific inhibitors e.g. antiphospholipid antibodies

3. Congenital intrinsic coagulation factors deficiencies: Contact pathway factors (prekallikrein, kallikrein, HMWK), FXII, FXI, FIX, FVIII

4. Specific inhibitors to one factor e.g. FVIII antibody

Prolonged PT and aPTT

1. Pre-analytical cause

     e.g. heparin contamination, under filling of tube

2. Drugs

     a. Direct or indirect inhibitory drugs e.g. direct thrombin inhibitors, heparin

     b. Supratherapeutic warfarin effect - FII, FVII, FIX, FX < 30%

3. Inhibitors

     a. Nonspecific inhibitor e.g. antiphospholipid antibodies

     b. Specific inhibitors to the common pathways (rare)

4. Decreased factor synthesis

     a. Congenital deficiency

     b. Reduced liver synthesis - Impaired production Fll, FV, FVII, FIX, FX, FXI, FXII, FXIII, dysfibrinogenemia

     c. Severe vitamin K deficiency ( decreased Fll, FVII, FIX, FX).

5. Factor consumption or binding

     a. Massive hemorrhage

     b. Disseminated intravascular coagulation (DIC)

     c. Factor X deficiency associated with systemic amyloidosis



- Jorge Cortés @Jcortesizaguirr



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