Bleeding time,clotting time, PT, and PTT

practical

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.

Hemostasis is maintained in the body via three mechanisms :

• Vascular spasm - Damaged blood vessels constrict.

• Platelet plug formation - Platelets adhere to damaged endothelium to form platelet plug (primary hemostasis) and then degranulate.

• Blood coagulation - Clots form upon the conversion of fibrinogen to fibrin, and its addition to the platelet plug (secondary hemostasis).

THE CLOTTING MECHANISM

INTRINSIC EXTRINSC

PROTHROMBIN THROMBIN

FIBRINOGEN

FIBRIN (II) (III)

(I) V

X

Tisue Thromboplastin Collagen

VII

XII

XI

IX

VIII

So What Causes Bleeding Disorders?

VESSEL DEFECTS

PLATELET DISORDERS

FACTOR DEFICIENCIES

LABORATORY EVALUATION

• PLATELET COUNT

• BLEEDING TIME (BT)

• Clotting time (CT)

• PROTHROMBIN TIME (PT)

• Activated PARTIAL THROMBOPLASTIN TIME (APTT)

PLATELET COUNT (CBC)

NORMAL 100,000 - 400,000 CELLS/MM3

< 100,000 Thrombocytopenia

50,000 - 100,000 Mild 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 Thromboplastin Collagen

VII

XII

XI

IX

VIII

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)

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 Thromboplastin Collagen

VII

XII

XI

IX

VIII

• 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