Purpose of the Test
To assess the extrinsic pathway of coagulation by measuring the clotting time of platelet poor plasma in the presence of tissue thromboplastin and calcium.
Principle
Tissue factor activates the extrinsic coagulation pathway, leading to the conversion of prothrombin to thrombin and fibrin clot formation. The time taken for clot formation is recorded as the PT.
Equipments
1. Coagulation analyzer
2. Test tubes
3. Pipettes
4. PT reagent
5. PT control plasma
Sample Type
Plasma in 3.2% sodium citrate in a 9:1 ratio
To Prepare the Sample Centrifuge at 1500 x g for 15 minutes.
Procedure
1. Transfer platelet poor plasma to labeled test tubes and incubate at 37°C for 2-3 minutes.
2. Take 100 μL of plasma in the cuvetter and put in the analyzer
3. Then add 200 μL PT reagent to test tube and simultaneously start the clot timer.
4. Stop the timer at first sign of fibrin clot formation. Record result in seconds.
| Test | |
|---|---|
| PT Reagent | 2000 μl |
| Plasma | 100 μl |
تختلف خطوات عمل التحليل حسب شركة المحلول المستخدم
Procedure
5. Report the result in Seconds and then calculate the INR
6. INR = (Patient PT / Mean Normal PT)ISI
Reference range: 11-13.5 seconds
Normal Range
Quality Control:
1. Run two levels of control with each batch of samples.
2. Results should fall within established confidence limits.
3. it is better to repeat the test at least 3 times and then determine the final result
Warning :
1. Improper blood collection can affect results.
2. Anticoagulant therapy prolongs PT.
M. Sulieman
mohammad@mlsgaate.com
Perform 2 levels of quality control before running patient samples.
QC results should fall within acceptable established range.
