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Prothrombin Time (PT)
• Name of the method:
Quick’s method
• Specimen:
Citrated plasma
Principle:-
• The prothrombin time is the time required for
the plasma to clot after addition of tissue
factor (thromboplastin) and an optimal
concentration of calcium.
• This indicates overall efficiency of extrinsic
pathway.
Requirements:-
• Water bath (37°C)
• Stop watch
• Test tubes
• Tissue thromboplastin
• 0.15 gm/dl Calcium chloride
• Platelets poor citrated plasma (PPCP) (mix 0.2 ml
of 3.8% tri-sodium citrate with 1.8 ml of blood)
prepared after centrifuging citrated blood at 3000
RPM for 15 minutes.
Procedure:-
1. Take 0.1 ml plasma in clean test tube. The
plasma should be pre-warmed at 37°C in
waterbath.
2. Add 0.1 ml tissue thromboplastin, mix well
and incubate at 37°C for 2 minutes.
3. Add 0.1 ml calcium chloride solution, mix and
start the stop watch.
4. At the first appearance of a fibrin clot, stop
the watch immediately.
5. Record the time.
6. Report prothrombin time in seconds.
Normal range:-
• 12-15 seconds
International normalized ratio (INR):-
• INR = (PT ratio)^ ISI of tissue thromboplastin
used.
• Normal range of INR= 1.0-1.2
• ISI = International sensitivity index.
• PT ratio= PT of test
PT of control
Clicinal significance:-
Prolonged PT is found in:-
- Oral anticoagulant therapy
- Vitamin K deficiency
- Liver disease
- Disseminated intravascular coagulation (DIC)
- Renal disease
- Deficiency of factors I, II, V, VII or X.
Sources of error:-
• Faulty collection of blood.
• Excess anticoagulant or insufficient
anticoagulant.
• Reagent not good.
• Glass tubes are not clean.
• Incorrect temperature of water bath. If
temperature is increased, factors may be
destroyed.
Prothrombin time

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Prothrombin time

  • 2. • Name of the method: Quick’s method • Specimen: Citrated plasma
  • 3. Principle:- • The prothrombin time is the time required for the plasma to clot after addition of tissue factor (thromboplastin) and an optimal concentration of calcium. • This indicates overall efficiency of extrinsic pathway.
  • 4. Requirements:- • Water bath (37°C) • Stop watch • Test tubes • Tissue thromboplastin • 0.15 gm/dl Calcium chloride • Platelets poor citrated plasma (PPCP) (mix 0.2 ml of 3.8% tri-sodium citrate with 1.8 ml of blood) prepared after centrifuging citrated blood at 3000 RPM for 15 minutes.
  • 5. Procedure:- 1. Take 0.1 ml plasma in clean test tube. The plasma should be pre-warmed at 37°C in waterbath. 2. Add 0.1 ml tissue thromboplastin, mix well and incubate at 37°C for 2 minutes. 3. Add 0.1 ml calcium chloride solution, mix and start the stop watch. 4. At the first appearance of a fibrin clot, stop the watch immediately.
  • 6. 5. Record the time. 6. Report prothrombin time in seconds.
  • 8. International normalized ratio (INR):- • INR = (PT ratio)^ ISI of tissue thromboplastin used. • Normal range of INR= 1.0-1.2 • ISI = International sensitivity index. • PT ratio= PT of test PT of control
  • 9. Clicinal significance:- Prolonged PT is found in:- - Oral anticoagulant therapy - Vitamin K deficiency - Liver disease - Disseminated intravascular coagulation (DIC) - Renal disease - Deficiency of factors I, II, V, VII or X.
  • 10. Sources of error:- • Faulty collection of blood. • Excess anticoagulant or insufficient anticoagulant. • Reagent not good. • Glass tubes are not clean. • Incorrect temperature of water bath. If temperature is increased, factors may be destroyed.