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
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
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.
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.