Coagulation disorderslaboratory approach

Establish whether bleeding is of recent origin (suggests acquired) or longstanding (congenital), spontaneous or induced by trauma/surgery, mucocutaneous ('platelet defect) or generalised ('coagulation defect or 'drug induced).

Laboratory tests

• FBC with platelet count, coagulation tests (PT, APTT, fibrinogen).

• Fill blood sample tube to the mark to ensure correct anticoagulant concentration.

• Repeat test if result abnormal before investigating further.

• Check patient not on anticoagulants.

Further investigation

Abnormal platelet count

• Both high and low counts may cause bleeding.

• If isolated low platelets ffl p384; if platelets high ffl p382.

• If platelets low and coagulation screen abnormal—could be DIC, liver disease, massive blood transfusion, primary blood disorder (e.g. leukaemia).

34g Abnormal coagulation result

^ PT 4 APTT normal

Warfarin, vitamin K deficiency, early liver disease, rarely congenital factor VII deficiency.

Warfarin overdose, vitamin K deficiency, liver failure, DIC. ^ PT normal APTT 4

Unfractionated heparin (UFH), haemophilia A or B, lupus anticoagulant, rarely vWD affects APTT, factor VIII inhibitors are rare but typically prolong APTT.

^ PT normal APTT normal

Normal PT and APTT do not exclude a significant bleeding tendency, for example effect of low molecular weight heparin, mild factor deficiency, platelet abnormality, or very rare factor deficiency such as factor XIII.

Further investigation

• DIC: check blood film, platelets, thrombin time, fibrinogen, XDPs/D-dimer.

• Vit K deficiency: assay VII and II; give vitamin K and repeat 24h later.

• Liver disease: check LFTs; will not correct to normal with vitamin K.

• Isolated factor deficiency: assay as indicated by PT/APTT results.

• Inhibitor-specific LA tests: check ACL; other factor-specific assays.

• Heparin: 4 APTT ratio, PT normal if APTT ratio 1.5-2.5, TT 4, repti-lase normal.

• Warfarin: PT prolongation>than APTT, low vitamin K dependent factors.

• vWD: diagnosis of von Willebrand disease requires measurement of vWF level and function. Note: bleeding time is neither sensitive nor specific for diagnosis or bleeding tendency.

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