Table 3

Initial and further investigations

Initial Investigation	Further investigation		Consider
PT	Isolated prolongation		Early warfarin therapy; early vitamin K deficiency, early liver disease. Possible factor VII deficiency
aPTT	Isolated prolongation: 50:50 plasma mix	Correction—factor deficiency, measure levels	Factor VIII or factor IX deficiency
	Isolated prolongation: 50:50 plasma mix	Correction—factor deficiency, measure levels	von Willebrand disease
			Factor XI deficiency (rare)
			Factor XII deficiency (not associated with bleeding)
		No correction—inhibitor	Lupus anticoagulant; heparin contamination
PT and APTT	Both prolonged (fibrinogen normal)		Warfarin, vitamin K deficiency, heparin
			Liver disease
			Rare factor deficiencies, e.g. II, V, X
Fibrinogen	Decreased	Prolonged PT and aPTT, decreased platelets	Disseminated intravascular coagulation
		Prolonged PT and aPTT, decreased platelets	Severe liver disease
		If <0.8 g/l, PT and aPTT will be prolonged	Dys/afibrinogenaemia
		Platelets normal
Thrombin time	Prolonged—reptilase time	Normal	Heparin
		Prolonged	as for low fibrinogen
Factor VIII	Low levels <40%		Haemophilia A
Factor IX	Low levels <40%		Haemophilia B
von Willebrand factor	Low antigen and/or activity (ristocetin co-factor) levels		von Willebrand disease