Bleeding time,clotting time, PT, and PTT

Ostadrahimi MD,PhD

Hemostasis or haemostasis : is a complex process which causes

the bleeding process to stop. It refers to the process of keeping blood within a damaged blood vessel.

THE CLOTTING MECHANISM

INTRINSIC EXTRINSC

PROTHROMBIN THROMBIN

FIBRINOGEN

FIBRIN(II) (III)

(I)V

X

Tisue ThromboplastinCollagen

VII

XII

XI

IXVIII

THROMBOCYTOPATHY )ADEQUATE NUMBER BUT ABNORMAL FUNCTION .(

causes UREMIA INHERITED DISORDERS MYELOPROLIFERATIVE DISORDERS

DRUG INDUCED(ASPIRIN, NSAIDS)

FACTOR DEFICIENCIES

Inherited:1. HEMOPHILIA A

2. HEMOPHILIA B

3. VON WILLEBRAND’S DISEASE

Acquired:

1. Anticoagulant therapy

2. Liver diseases

3. DIC

LABORATORY EVALUATION

PLATELET COUNTBLEEDING TIME (BT)PROTHROMBIN TIME (PT)PARTIAL THROMBOPLASTIN TIME (PTT)THROMBIN TIME (TT)

PLATELET COUNT (CBC)

NORMAL 100,000 - 400,000 CELLS/MM3

<100,000 Thrombocytopenia

50,000 - 100,000Mild Thrombocytopenia

<50,000 Sever Thrombocytopenia

BLEEDING TIME

PROVIDES ASSESSMENT OF PLATELET COUNT AND FUNCTION

NORMAL VALUE

2-8 MINUTES

PROTHROMBIN TIME

Measures Effectiveness of the Extrinsic Pathway

NORMAL VALUE

10-15 SECS

PT The prothrombin time: is therefore the time required for the

plasma to clot after an excess of thromboplastin and an optimal concentration of calcium have been added.

Measures the function of the Extrinsic Pathway. Sensitive to Factors I, II, V, VII, X.

The PT evaluates patients suspected of having an inherited or acquired deficiency in these pathways.

THE CLOTTING MECHANISM

INTRINSIC EXTRINSC

PROTHROMBIN THROMBIN

FIBRINOGEN

FIBRIN(II) (III)

(I)V

X

Tisue ThromboplastinCollagen

VII

XII

XI

IXVIII

When is it ordered?

Used to monitor oral anticoagulant therapy (Warfarin / Coumadin).

When a patient who is not taking anti-coagulant drugs has signs or symptoms of a bleeding disorder.

When a patient is to undergo an invasive medical procedure, such as surgery, to ensure normal clotting ability.

An elevated prothrombin time may indicate the presence of:

Vitamin K deficiency(Vitamin K is needed to make prothrombin and other clotting factors)

DIC liver disease a deficiency in one or more of the following factors: I, II, V, VII, X. Anticoagulant (warfarin)

INR

A PT test may also be called an INR test. INR (international normalized ratio) stands for a way of

standardizing the results of prothrombin time tests, no matter the testing method.

So your doctor can understand results in the same way even when they come from different labs and different test methods.

Using the INR system, treatment with (anticoagulant therapy) will be the same. In some labs, only the INR is reported and the PT is not reported

An INR of 1.0 means that the patient PT is normal. An INR greater than 1.0 means the clotting time is

elevated. INR of greater than 5 or 5.5 = unacceptable high risk of

bleeding,whereas if the INR=0.5 then there is a high chance of having a clot.

Normal range for a healthy person is 0.9–1.3, and for people on warfarin therapy, 2.0–3.0, although the target INR may be higher in particular situations, such as for those with a mechanical heart valve.

PARTIAL THROMBOPLASTIN TIME

Measures Effectiveness of the Intrinsic

Pathway

NORMAL VALUE

25-40 SECS

PTT

The partial thromboplastin time (PTT) or activated partial thromboplastin time (aPTT or APTT( is a performance indicator measuring the efficacy of both the "intrinsic" and the common coagulation pathways.

It is also used to monitor the treatment effects with heparin a major anticoagulant.

Kaolin cephalin clotting time (KccT) is a historic name for

the activated partial thromboplastin time

THE CLOTTING MECHANISM

INTRINSIC EXTRINSC

PROTHROMBIN THROMBIN

FIBRINOGEN

FIBRIN(II) (III)

(I)V

X

Tisue ThromboplastinCollagen

VII

XII

XI

IXVIII

Normal PTT times require the presence of the following coagulation factors:

I, II, III, IV, V, VI, VIII, IX, X, XI, & XII

When is it ordered?

When a patient presents with unexplained bleeding or bruising,

It may be ordered as part of a pre-surgical evaluation for

bleeding tendencies,

When a patient is on intravenous (IV) or injection heparin

therapy, the APTT is ordered at regular intervals to monitor the degree of anticoagulation.

Prolonged APTT may indicate:

use of heparin.

antiphospholipid antibody:especially lupus anticoagulant, which paradoxically increases propensity to thrombosis

coagulation factor deficiency ,

e.g hemophilia DIC Liver disease

THE CLOTTING MECHANISM

INTRINSIC EXTRINSC

PROTHROMBIN THROMBIN

FIBRINOGEN

FIBRIN(II) (III)

(I)V

X

Tisue ThromboplastinCollagen

VII

XII

XI

IXVIII

FACTOR DEFICIENCIES

Inherited:1. HEMOPHILIA A

2. HEMOPHILIA B

3. VON WILLEBRAND’S DISEASE

Acquired:

1. Anticoagulant therapy

2. Liver diseases

3. DIC

HEMOPHILIA A (Classic Hemophilia)80-85% of all HemophiliacsDeficiency of Factor VIIILab Results - Prolonged PTT

HEMOPHILIA B (Christmas Disease)10-15% of all HemophiliacsDeficiency of Factor IXLab Test - Prolonged PTT

VON WILLEBRAND’S DISEASEDeficiency of VWF & amount of Factor VIIIFactor VIII is bound to vWF while inactive in

circulation; Factor VIII degrades rapidly when not bound to vWF

Lab Results - Prolonged BT, PTT

ANTICOAGULANTS

An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting

This prevents deep vein thrombosis, pulmonar embolism, myocardial infarction and stroke.

ANTICOAGULANTS1. Coumadins (Vitamin K antagonists)2. Heparin

Coumadins

These oral anticoagulants that antagonize the effects of vitamin K.

Examples include warfarin. It takes at least 48 to 72 hours for the anticoagulant effect to develop. Where an immediate effect is required, heparin must be given concomitantly.

Monitored by PT times These anticoagulants are used to treat patients

with deep-vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation (AF), and mechanical prosthetic heart valves.

Heparin

Heparin is a biological substance. It works by activating antithrombin III, which

blocks thrombin from clotting blood. Heparin Therapy is Monitored by PTT times Low molecular weight heparin is a more highly

processed product that is useful as it does not require monitoring of the APTT coagulation parameter (it has more predictable plasma levels) and has fewer side effects.

Liver Disease

Liver Disease can Result in Reduced Production of Coagulation Factors (I,II,V,VII,IX,X).

DIC

Disseminated intravascular coagulation (DIC is a pathological activation of coagulation) blood clotting) mechanisms that happens in response to a variety of diseases

DIC leads to the formation of small blood clots inside the blood vessels throughout the body

The small clots also disrupt normal blood flow to organs (such as the kidneys), which may

malfunction as a result

As the small clots consume coagulation proteins and platelets, normal coagulation is disrupted and abnormal bleeding occurs from the skin the gastrointestinal tract, the respiratory tract and

surgical wounds. The PT and APTT are usually very prolonged and

the fibrinogen level markedly reduced High levels of fibrin degradation products,

including D-dimer, are found owing to the intense fibrinolytic activity stimulated by the presence of

fibrin in the circulation.

Definitive diagnosis depends on the result of DIC:

Thrombocytopenia) prolonged bleeding time) Prolongation of prothrombin time and activated

partial thromboplastin time A low fibrinogen concentration Increased levels of fibrin degradation products

Platelet count  

Bleeding time  

Partial thromboplastin time  

Prothrombin time  

Condition  

unaffected prolonged prolonged unaffected Von Willebrand disease

unaffected unaffected prolonged prolongedVitamin K deficiency or Warfarin

unaffected prolonged unaffected unaffected Uremia

unaffected unaffected prolonged unaffected Haemophilia

unaffected unaffected prolonged prolonged Factor V deficiency

unaffected prolonged unaffected unaffected Aspirin

decreased prolonged unaffected unaffected Thrombocytopenia

decreased prolonged prolonged prolonged End-stage Liver failure

decreased prolonged prolonged prolongedDisseminated intravascular coagulation

decreased prolonged unaffected unaffected Bernard-Soulier syndrome

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