Coagulation Profile

OVERVIEW

• Prothrombin Time
• Activated Partial Thromboplastin Time
• Thrombin Time
• Fibrinogen
• Fibrin Degradation Products (FDP’s)
• APTT 50% NP
• Retiplase Time
• Euglobin Lysis Time
• Urea solubility Test

PROTHROMBIN TIME

• thromboplastin added
• tests the extrinsic pathway
• ratio compared to control (INR)
• tests factors: I, II, V, VII, X

-> warfarin
-> vitamin K deficiency
-> liver disease
-> DIC
-> artefact: incorrect sampling or increased haematocrit (> 55%)

ACTIVATED PARTIAL THROMBOPLASTIN TIME

• kaolin added
• tests intrinsic pathway
• tests factors: I, II, V, VIII, IX, XI, XII

-> heparin
-> DIC
-> haemophilia
-> liver disease

THROMBIN TIME

• thrombin added to undiluted plasma
• tests the conversion of fibrinogen -> fibrin
• prolonged in:

-> heparin
-> DIC
-> hypofibrinogenaemia
-> fibrin degradation products

FIBRINOGEN

• normal: 1.5-4.0
• high in: acute phase response
• low in:

-> sepsis
-> DIC

FIBRIN DEGRADATION PRODUCTS (FDPs)

• marker of fibrin and fibrinogen breakdown

APTT 50% NP

• mixing of patients sample with pooled normal plasma – 50:50 mix
• failure to correct after mixing:

-> lupus anticoagulant present (should go on to autoantibodies and anti-cardiolipin antibodies)

ECHIS TIME

• snake venom from Echis multisquamatus added to sample
• differentiates liver dysfunction from vitamin deficiency
• this activates prothrombin without requiring vitamin K
• is normal in vitamin K deficiency or warfarin use
• if prolonged:

-> factor deficiency (liver disease)

RETIPLASE TIME

• used to detect deficiency or abnormalities in fibrinogen
• snake venom that has similar action to thrombin but is resistant to inhibition by antithrombin III
• interpret with TCT
• if retiplase time normal and TCT prolonged:

-> heparin
-> hirudin
-> direct thrombin inhibitors

EUGLOBIN LYSIS TIME

• shortened time:

-> presence of systemic fibrinolytic pathway activators

UREA SOLUBILITY TEST

• factor 13 stabilises fibrin
• if deficient 5M urea will dissolve it