activated partial thromboplastin time

time (tīm) a measure of duration. Symbol t.

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activated partial thromboplastin time  (APTT) (aPTT) (PTT) the period required for clot formation in recalcified blood plasma after contact activation and the addition of platelet substitutes; used to address the intrinsic and common pathways of coagulation.

bleeding time  the duration of bleeding after controlled, standardized puncture of the earlobe or forearm; a relatively inconsistent measure of capillary and platelet function.

circulation time  the time required for blood to flow between two given points.

clotting time , coagulation time the time required for blood to clot in a glass tube.

inertia time  the time required to overcome the inertia of a muscle after reception of a stimulus from a nerve.

one-stage prothrombin time  prothrombin t.

prothrombin time  (PT) the rate at which prothrombin is converted to thrombin in citrated blood with added calcium; used to assess the extrinsic coagulation system of the blood.

reaction time  the time elapsing between the application of a stimulus and the resulting reaction.

stimulus-response time  reaction t.

thrombin time  (TT) the time required for plasma fibrinogen to form thrombin, measured as the time for clot formation after exogenous thrombin is added to citrated plasma.

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Activated partial thromboplastin time

Partial thromboplastin time test that uses activators to shorten the clotting time, making it more useful for heparin monitoring.

Mentioned in: Partial Thromboplastin Time

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activated partial thromboplastin time (APTT).

See partial thromboplastin time.

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thromboplastin

a substance in blood and tissues which, in the presence of ionized calcium, aids in the conversion of prothrombin to thrombin. Extrinsic and intrinsic thromboplastin are formed as the result of the interaction of different clotting factors; the factors that combine to form extrinsic thromboplastin are not all derived from intravascular sources, whereas those that form intrinsic thromboplastin are.

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activated partial thromboplastin time

see activated partial thromboplastin time.

extrinsic thromboplastin

the prothrombin activator formed as a result of interaction of coagulation factors III, VII, and X which, with factor IV, aids in the formation of thrombin.

thromboplastin generation time (TGT)

evaluates the first stage in blood coagulation by measuring the efficiency of prothrombinase formation.

intrinsic thromboplastin

the prothrombin activator formed as a result of interaction of coagulation factors V, VII, IX, X, XI and XII and platelet factor 3 (PF-3), which, with factor IV, aids in the conversion of prothrombin to thrombin.

plasma thromboplastin antecedent (PTA)

clotting factor XI; deficiency occurs in cattle and dogs, causing mild to severe bleeding tendencies called hemophilia C.

plasma thromboplastin component (PTC)

clotting factor IX; deficiency causes christmas disease. Called also Christmas factor, antihemophilic factor B, autoprothrombin II.

thromboplastin time

see activated partial thromboplastin time.

tissue thromboplastin

factor III, a material derived from several sources in the body (e.g. brain, lung), and is important in the formation of extrinsic prothrombin converting principle in the extrinsic pathway of blood coagulation. Called also tissue factor.

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activated partial thromboplastin time

aPTT Hematology A test that evaluates the clotting factors of the intrinsic pathway–except VII and XIII, by measuring the time required to form a fibrin clot; aPTT is used to screen for bleeding tendencies and to monitor heparin therapy; it is ↑ in coagulation factor deficiencies–factors V, VIII, IX, X, XI, XII, DIC, Hodgkin's disease, hypofibrinogenemia, leukemia, cirrhosis, vitamin K deficiency, von Willebrand's disease, and in drug therapy–eg, heparin and aspirin Ref range 30-40 secs. See Prothrombin time.