COAGULATION TESTS

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COAGULATION TESTS
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• PT
• PTT
• Fibrinogen

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Equipment

• Water bath
• Centrifuge
• Reagents Buffers
• Plastic glass tube
• Pipettes
• Stopwatches
• Automated coagulation analyzers

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PreAnalytical variables

• Collection of venous blood
• Exessive stress, Tourniquet, Needle
• Anticoagulant
  Trisodium
  citrate(3.2 0.109 mol/L ) nine volume
  of blood added to one volume of anticoagulants
• Under over filling of tubes
• Severe anemia, polycytemia

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PreAnalytical variables(cont.)

• Centrifugation
  2000 g 15 min 4oC
• Storage of sample
• Time of sample collection
• Icteric , Lipemic plasma-Hemolysis-Clot formation

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Analytical variables

• Sample , Delay in sample processing
• Equipment
• Reagents )thromboplastin , Ca )
• Contamination of the reagents
• Test method

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Quality Control

• Control plasma(normal abnormal)
• Pooled plasma
• EQAS

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Prothrombin Time (PT)
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Prothrombin Time (PT)

• Samples should be stored in room temprature
• Reagent is Thromboplastine
• Expression of results
• Normal Reference Range

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Thromboplastine

• Tissue factor Apoprotein,Phospholipid
• Source of Tissue Factor
• rabbit ,human ,monkey brain
• rabbit lung, human placenta
• Recombinant

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• International Normalized Ratio (INR) system was
  introduced by the WHO in 1983
• International Sensitivity Index (ISI)
• patient PT
• INR( )
  
• mean of normal PT
  

ISI
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Therapeutic Range
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ISI

• The lower the ISI value the more sensitive the
  reagent.(0.9-1.7)
• Use of reagents with lower ISI,s improve the
  precision of INR.

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(PT increasing from 23 secs to 25 secs will
increase the INR 23
1 25 1
ISI 1 ( )2.1
( ) 2.4
10.5 10.5 ISI 2
23 2 25
2 ( )4.8
( )5.7
10.5
10.5
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• a variation in the time of clot detection will
  result in amplification in INR calculation
  by higher ISI value.
• Loss of accuracy and precision with insensitive
  Thromboplastin (ISIgt1.5)
• Insensitive Thromboplastin caused low PT ratio

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• Thromboplastine reagents with low ISI will result
  in a longer PT.

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Choice of Thromboplastine

• The lower the ISI value the more sensitive the
  reagent.
• Use of reagents with lower ISI,s improve the
  precision and accuracy of INR.
• Use of Thromboplastine with ISI
• 0.9-1.7 is highly recommended

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Activated Partial ThrombineTime (PTT)

• Sample Storage
• Reagent
  Contact factor,Ca
• Method
• Ca 0.025 mol/l
• Normal Reference Range
• Expression of results

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Fibrinogen Assay

• Reagents
  Fibrinogen Standard
• Thrombin solution
• Owren Buffer
• Calibration curve

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Coagulation Analyzer

• Electromechanical
• Photooptical
• Electrochemical

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