Test 3: PT (Prothrombin Time)

Question 1

What is used for the Electromechanical Detection of Clot Formation?

Answer 1

Fibrometer

Question 2

The Fibrometer system is composed of what 3 parts?

Answer 2

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.

Question 3

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.

Answer 3

Fibrometer

Question 4

Photo-Optical Detection of Clot Formation:

Soluble Fbg = __________ light transmittance

Insoluble fibrin clot = _________ light scatter

Answer 4

Increased, increased

Question 5

Equipment needed for PT test

Answer 5

1. BFT II Analyzer
2. Automated pipet & tips
3. BFT II sample cuvettes 5. Innovin*
4. Normal and abnormal controls
5. Na-citrated patient samples

Question 6

All samples are run in duplicate & the clotting times are averaged to yield the final result. Your precision should agree within _____ seconds.

Answer 6

+/- 2.0

Question 7

normal range for PT?

Answer 7

11 - 13 seconds

Question 8

The prothrombin time screens for deficiencies in the extrinsic coagulation pathway (Factors _______________) & is also used to monitor oral anticoagulant drug therapy (warfarin & coumarin

Answer 8

(Factors 1, 2, 5, 7 & 10),

Question 9

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.

Answer 9

vitamin K’s

Question 10

Testing must be performed within ____ hours after specimen is drawn if held at room temp., & within _____days if plasma is stored at -20oC.

Answer 10

2, 2-5

Question 11

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.)

Answer 11

2.0-3.0, 2

Question 12

What does INR stand for?

Answer 12

International Normalized Ratio

Question 13

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?

Answer 13

different thromboplastins do not have the same sensitivity; in addition, the methodology used to assay the sample can significantly affect the result.

Question 14

a method of monitoring patients on oral anticoagulants using a new value devised by The World Health Organization

Answer 14

International Normalized Ratio (INR)

Question 15

INR =

Answer 15

(Patient’s Average PT result / Avg. PT of Normal Range QC in your lab)

Question 16

This term, (Patient’s Avg. PT result / Avg. PT of N. R. QC in your lab), is called the…

Answer 16

PT ratio

Question 17

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.

Answer 17

International Sensitivity Index (ISI)

Question 18

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 _____).

Answer 18

INR

Question 19

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.)

Answer 19

PT ratio

Question 20

With the INR, it is possible to obtain more consistent and meaningful results on patients receiving __________ therapy

Answer 20

anticoagulant

Question 21

Using the _____ decreases or eliminates differences seen between labs

Answer 21

INR

Question 22

INR =

Answer 22

(Patient’s PT / Mean N.R. of QC )

• must be able to calculate on exam

Question 23

Criteria for Specimen Rejection in Coagulation Testing..

Answer 23

-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

Question 24

NEVER RECONSTITUTE ANYTHING WITH WATER FROM A SQUIRT BOTTLE!
ALWAYS USE ____________FROM THE TAP!

Answer 24

FRESH DI WATER