Test 3: PT (Prothrombin Time) Flashcards
What is used for the Electromechanical Detection of Clot Formation?
Fibrometer
The Fibrometer system is composed of what 3 parts?
a mechanical mixer-timer block, a heat block (for prewarming reagents & samples to 37o C), & an automated pipet to deliver sample or reagent into the test cuvette.
The ____________ probe, which is part of the timer, serves as the clot detector. It measures conductance of an electric current generated by formation of the fibrin clot.
Fibrometer
Photo-Optical Detection of Clot Formation:
Soluble Fbg = __________ light transmittance
Insoluble fibrin clot = _________ light scatter
Increased, increased
Equipment needed for PT test
- BFT II Analyzer
- Automated pipet & tips
- BFT II sample cuvettes 5. Innovin*
- Normal and abnormal controls
- Na-citrated patient samples
All samples are run in duplicate & the clotting times are averaged to yield the final result. Your precision should agree within _____ seconds.
+/- 2.0
normal range for PT?
11 - 13 seconds
The prothrombin time screens for deficiencies in the extrinsic coagulation pathway (Factors _______________) & is also used to monitor oral anticoagulant drug therapy (warfarin & coumarin
(Factors 1, 2, 5, 7 & 10),
Coumarin/coumadin/warfarin depresses the liver’s production of Factors 2, 7, 9 & 10 by interfering with ___________ activation of these factors. Since the PT measures 3 of these 5 factors, it can be used to monitor these drugs’ effects.
vitamin K’s
Testing must be performed within ____ hours after specimen is drawn if held at room temp., & within _____days if plasma is stored at -20oC.
2, 2-5
Patients receiving oral anticoagulants have their doses targeted to achieve an INR of _____ (The greater the INR, the more anticoagulated the blood is. So an INR of < _____ means the blood is not anticoagulated enough.)
2.0-3.0, 2
What does INR stand for?
International Normalized Ratio
Why would a 12.5 sec result at one hospital not equate to a 12.5 sec result elsewhere, regardless of whether or not the run was in control?
different thromboplastins do not have the same sensitivity; in addition, the methodology used to assay the sample can significantly affect the result.
a method of monitoring patients on oral anticoagulants using a new value devised by The World Health Organization
International Normalized Ratio (INR)
INR =
(Patient’s Average PT result / Avg. PT of Normal Range QC in your lab)
This term, (Patient’s Avg. PT result / Avg. PT of N. R. QC in your lab), is called the…
PT ratio
WHO developed an international reference thromboplastin reagent. It was given a value of 1.0. All of the various thromboplastin manufacturers now calibrate each lot number of their reagent against this standardized WHO thromboplastin. The results are used to develop an ______________ value for that batch of reagent.
International Sensitivity Index (ISI)
International Sensitivity Index (ISI) numbers are published in the reagent’s package insert in the form of a table (so that the PT ratio & the ISI can be used to look up the _____).
INR
INR can be considered to be the __________ if the test had been performed using the WHO thromboplastin reagent. (Ratio of patient’s PT to average control PT has long been used in anticoagulant monitoring.)
PT ratio
With the INR, it is possible to obtain more consistent and meaningful results on patients receiving __________ therapy
anticoagulant
Using the _____ decreases or eliminates differences seen between labs
INR
INR =
(Patient’s PT / Mean N.R. of QC )
- must be able to calculate on exam
Criteria for Specimen Rejection in Coagulation Testing..
-More than 2 hours at room temp.
-Exposure to extremes of temperature (degrades which Coag factors 1st? ____________)
-Blue top tube < 90% full! (Unlike purple tops!!!)
-Clotted Specimen
-Specimen hemolyzed
NEVER RECONSTITUTE ANYTHING WITH WATER FROM A SQUIRT BOTTLE!
ALWAYS USE ____________FROM THE TAP!
FRESH DI WATER
