CLINICAL LAB SCIENEC

360
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
Calculation
Total of Side 1 Total of Side 2 divided by 2 total count average
Average (average 0.1) 100 _______________________ cells/μL
Average (average 0.1) 10,000 _______________________ cells/L (SI Units)
Comments (unusual findings) _____________________________________________________
Performed by: _______________________ Date Reported _________________________
HEMATOLOGY AND COAGULATION PROCEDURE #8
Manual Prothrombin Time (PT)
Principles
Most prothrombin coagulation tests are performed with automated equipment, but it
is important for the student to understand the determination of certain clotting factors
that affect the formation of a fibrin clot. The beginner can easily visualize the formation
of the clot in a glass tube when a patient sample or control is combined with the
proper reagent. The one-stage PT measures the clotting time of plasma after adding
a source of tissue factor (thromboplastin) and calcium. The recalcification of plasma
in the presence of added tissue factors generates activated factor X. This in turn activates
prothrombin to thrombin, which converts fibrinogen to an insoluble but visible
fibrin clot.
Equipment and Supplies
1. Gloves, disposable paper towels, and disinfectant or other cleaning solution
2. Report form for Procedure #8
3. Citrated blood sample that has been centrifuged. The plasma should be removed
from the blood cells for testing
4. Control samples reconstituted with deionized water
5. 13 100 test tubes and test tube rack
6. Water bath or heat block set at 37°C
7. Pipetters and tips to measure 0.1 and 0.2 mL
8. Electronic timing device or clock/watch with second hand
Procedure
1. Wash hands and don gloves.
2. Assemble necessary equipment and supplies.
3. Dispense 0.1 mL of citrated plasma into 13 100 mm test tubes, one for each
sample and control.
4. Prewarm all tubes (samples, controls) and the pool of thromboplastin in the heat
block to 37°C.
5. Place 0. 2 mL warmed thromboplastin into a tube containing the citrated plasma
sample.
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