Disorders of hemostasis

Disorders of Hemostasis
Hemostatic disorders can be inherited or acquired. Acquired disorders are by far the most common, particularly thrombocytopenia.
The table below summarizes the usual laboratory results seen in many diseases affecting hemostasis.

Disorder	ACT*	aPTT	PT	TCT**	FIBR	FDPs or D-dimer	PLTs	Confirming Tests
Trauma	N	N	N	N	N, I	N, I#	N, D	History, PE, imaging, etc.
Thrombocytopenia	N	N	N	N	N	N, I#	D	Platelet count, often <30,000/ul
Anticoag. rodenticide Vitamin K lack	N, I	I	I	N	N	N, I#	N, D	Improvement with vitamin K1
DIC	N, I	I	N,I	I	D, N, I	I	D	No confirmatory test - identify initiating disease
Severe liver disease	N, I	I	I	N, I	D, N	N, I	N, D	Liver biopsy, imaging
vWD	N	N	N	N	N	N	N	Decreased vWf:Ag
Intrinsic factor deficiency: factor VIII factor IX factor XI factor XII Prekallikrein	N, I N, I N, I N, I N	I I I I I	N N N N N	N N N N N	N N N N N	N, I# N, I# N, I# N N	N N N N N	Factor assay
Extrinsic factor deficiency: factor VII	N	N	I	N	N	N	N	Factor assay
Common factor deficiency: factor X factor II	N, I	I	I	N	N	N, I	N, I	Factor assay
Dysfibrinogenemia	N, I	I	I	I	D, N	N, I#	N	Normal fibrinogen:Ag
Monoclonal Gammopathy	N, I	N, I	N,I	N	N	N	D, N	Serum protein electrophoresis, Radial immunodiffusion
Congenital platelet function defect	N	N	N	N	N	N	N	Platelet function testing

ACT: Activated coagulation time; aPTT: Activated partial thromboplastin time; PT: Prothrombin time; TCT: Thrombin clot time; FIBGEN: Fibrinogen concentration determined in clotting assays (functional fibrinogen); Plts: Platelets; FDPs: Fibrin(ogen) degradation products; DIC: Disseminated intravascular coagulation; vWD: von Willebrand Disease; N: Normal; D: Decreased; I: Increased.

* The ACT is less sensitive to factor deficiencies than the aPTT, therefore the aPTT may be prolonged whilst the ACT may be normal in the same disorder. The ACT also requires platelets from the patient as the source of the phospholipid needed to support clotting. Therefore, severe thrombocytopenia (platelet count < 10,000/mL) may mildly prolong the ACT. In contrast, an exogenous source of phospholipid is added to the aPTT reagent, making this test independent of the patient's platelets.

** FDPs and D-dimer may be increased in any condition associated with severe hemorrhage into tissue or body cavities.

# The TCT measures the ability of a standard concentration of thrombin to convert the patient's fibrinogen to fibrin. In general, a prolonged TCT indicates a hypofibrinogenemia and/or dysfibrinogenemia. The latter indicates that fibrinogen is abnormal or there are factors interfering with fibrin polymerization, such as heparin therapy or circulating FDPs. These will cause a prolonged TCT but a fibrinogen concentration may be normal. Remember that fibrinogen is an acute phase reactant protein and will increase with inflammation. Since inflammation is a common cause of DIC, fibrinogen concentrations will represent the balance between consumption (decreasing values) and inflammation (increasing values).