Kamlesh Darji/X

Aug 26, 2026, 17:52

Kamlesh Darji: A Practical Guide to Interpreting Coagulation Tests

Kamlesh Darji, Senior Resident in the Department of Pathology at AIIMS (All India Institute of Medical Sciences), shared a post on X:

“He four core patterns

Prolonged APTT with normal PT : hemophilia A/B, factor 11 or 12 deficiency, lupus anticoagulant; vWD may prolong APTT if factor 8 is reduced
Prolonged PT with normal APTT : factor 7 deficiency, early warfarin effect, early vitamin K deficiency, early liver disease
Both PT and APTT prolonged : DIC, severe liver disease, severe vitamin K deficiency, common pathway factor deficiency
Both PT and APTT normal with bleeding : platelet function disorder, mild vWD, factor 13 deficiency, vascular disorder

Mixing study: The Splitter

Corrects on mixing : factor deficiency
Does not correct on mixing : inhibitor such as lupus anticoagulant or specific factor inhibitor
Factor 8 inhibitor : may initially correct but fail to correct after incubation because the inhibitor is time dependent

Platelet disorders

Low platelets with large young platelets and normal/increased marrow megakaryocytes : immune thrombocytopenia
Low platelets with schistocytes and normal coagulation tests : TTP or HUS
Low platelets with schistocytes and deranged coagulation tests : DIC
Platelet fall typically 5–10 days after heparin with thrombosis : heparin-induced thrombocytopenia
Usually normal platelet count with reduced VWF antigen/activity : von Willebrand disease
Reduced ristocetin-induced platelet agglutination corrected by normal plasma : von Willebrand disease
Reduced ristocetin-induced platelet agglutination not corrected by normal plasma : Bernard-Soulier syndrome
Normal ristocetin response with defective aggregation to ADP, epinephrine and collagen : Glanzmann thrombasthenia
Giant platelets with thrombocytopenia : Bernard-Soulier syndrome
Small platelets with eczema and immunodeficiency : Wiskott-Aldrich syndrome

Factor deficiencies

Factor 8 deficiency : hemophilia A, X-linked
Factor 9 deficiency : hemophilia B, X-linked
Factor 11 deficiency : hemophilia C, classically associated with Ashkenazi Jewish ancestry
Factor 12 deficiency : markedly prolonged APTT without clinical bleeding
Factor 13 deficiency : normal PT and APTT with delayed bleeding; diagnose with factor 13 activity assay
Vitamin K-dependent factors : 2, 7, 9, 10, protein C and protein S
Shortest half-life among vitamin K-dependent clotting factors : factor 7, therefore PT rises first

Highest Yield Information

Warfarin-induced skin necrosis : rapid fall in protein C, especially in underlying protein C deficiency
Arterial or venous thrombosis with recurrent pregnancy morbidity : antiphospholipid syndrome
Prolonged APTT that fails to correct on mixing with thrombosis : lupus anticoagulant
Thrombosis with intravascular hemolysis and cytopenias : paroxysmal nocturnal hemoglobinuria
Heparin resistance : consider antithrombin deficiency, although several acquired causes also occur
Homocystinuria with thrombosis : cystathionine beta-synthase deficiency

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