Quick´s prothrombin time determination
This test measures the activity of the extrinsic pathway of coagulation.
We will need: a marker, equipment for venous blood sampling,
a glass hook, automatic pipettes, glass test tubes,
activated tissue factor (factor 3) = thromboplastin, calcium chloride, sodium citrate, a heated bath and a stopwatch
We take 2.7 ml of venous blood in a syringe with 0.3 ml of sodium citrate.
Sodium citrate chelates calcium from blood, disrupting the coagulation.
Only blood plasma is used for the test.
After the elements are properly mixed we centrifuge them.
After centrifugation, the separated plasma is transferred in a new test tube.
The plasma in one and the other reagents in a different test tube are incubated at 37°C in a heated bath
After incubation, 0.1 ml of the blood plasma is transferred by a pipette to a new test tube.
afterwards, using a new pipette tip we add 0.2 ml of activated tissue factor and
calcium chloride which provides an excess of calcium ions.
We turn the stopwatch on imediatelly.
We are constantly checking the contents of the test tube for fibrin fibres with a glass hook.
As we find fibrin fibres we turn the stopwatch off.
Physiological values for the prothrombin time are in range of 11 - 16 seconds.
The test is repeated with the same sample 2-3 times and we calculate the avarege value.