Coagulation Instrumentation

Question 1

Clot formation was determined by visual inspection of the plasma as the tube was tilted, and a stopwatch was used to determine the time to clot formation. This was referred to as the

Answer 1

Tilt-tube technique

Question 2

The 1950s witnessed the dawn of the modern era of instru- mentation in coagulation testing with the development of the first coagulometer

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BBL Fibrometer.

Question 3

Subsequent 20th century developments in clot detectors in- cluded a

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rolling steel ball and photo-optical measurements

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Coagulation instruments apply clot detection principles that either

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observe” the clot formation (optical and nephelometric devices)
detect the clot by “feel” (mechanical and viscosity- based devices).

Question 5

detect a change in plasma optical density (OD; light transmittance) during the clotting process.

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Photo-optical (turbidometric) coagulometers

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Principle of photo optical

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LIGHT TRANSMITTANCE

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used to detect clot formation in the past is still used today in particular instruments for whole blood clotting.

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viscoelastic technique

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vital for assesing hemostasis

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viscoelastic technique

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Chromogenic (synthetic substrate, amidolytic) methodology uses a synthetic small peptide substrate conjugated to a chromo- phore, usually

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para-nitroaniline (pNA).

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means for measuring the activity of a specific coagulation fac- tor because it exploits the factor’s enzymatic (protease) proper- ties.

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Chromogenic analysis

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The activity of coagulation enzymes is measured by

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direct or indirect chromogenic methods

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a modification of photo-optical end-point detection in which 90-degree or forward-angle light scatter, rather than OD, is measured.

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Nephelometry

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and a photodetector detects variations in

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light scatter at 90 degrees (side scatter)
180 degrees (forward-angle scatter)

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be adapted to measure the dynamics or kinetics of clot formation.

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Nephelometry

Question 15

are the newest assays available for routine coagulation testing.

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Immunologic assays

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ASSAY END-POINT DETECTION PRINCIPLES

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Mechanical Clot End-Point Detection
Photo-Optical Clot End-Point Detection
Viscoelastic Clot Detection
Nephelometric End-Point Detection
Immunologic Light Absorbance End-Point Detection
Chromogenic End-Point Detection

Question 17

Tradi- tionally, PT assays required. (Reagent and specimen volume)

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100 ul of patient plasma and 200 uL of thromboplastin/calcium chloride reagent

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flexibility of selecting reagents that best suit their needs, and prefer not to be restricted in their choicesby the analyzer being used.

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Open Reagent Systems

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has improved the safety and efficiency of coagulation testing.

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Closed-tube sampling of specimens

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premature activation of coagulation factors and platelets
that generate FVIIa and thrombin.

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Clotted

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OD-sensing instruments because of interference with light
transmittance.

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Lipemia
Hemolysis

Question 22

Causes falsely shortened

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Clotted
Hemolysis

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Falsely prolonged

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Icterus
Lipemia

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Falsely elevated

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Abnormal clot formation

Question 25

A second common POC test is the

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prothrombin time/ international normalized ratio (PT/INR) f

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technique uses the viscoelastic property of blood clotting

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Thromboelastography

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The assay pro- vides information on the entire kinetic process of whole blood clot formation.

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Thromboelastography

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Clot initiation or clotting time

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TEG- R ROTEM- CT Comment- Time of initial fibrin formation

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Clot kinetics

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TEG- K ROTEM- CFT (clot formation time) COMMENT- measure of the speed to reach a specific level of clot strength

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📐

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TEG- a ROTEM- a COMMENT- Measure of the rate of clot formation, reflects the rate of fibrin formation and cross linking

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Clot strength

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TEG- MA (maximum amplitutde) ROTEM- MCF (maximum clot firmness COMMENT- Measure of the strength of the clot

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Clot stability

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TEG- Ly30 (lysis at 30 minutes as a ratio of MA) ROTEM- CLI (clot lysis index) COMMENT- Measure of the rate of amplitude reduction

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Platelet Aggregometers principle

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Light transmittance

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This test system measures the increase in light transmission that occurs in direct propor- tion to platelet aggregation

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Platelet Aggregometers

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mea- suring the platelet secretion response using the luciferase reagent

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Chrono-Log has a Whole Blood/Optical Lumi-Aggregation

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Chronolog principle

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Electrical impedance

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used to detect aggregation, and optical density to detect luminescence identifies platelet secretion.

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Electrical impedance

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monitors platelet function by impedance, is the latest development.2

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Multiplate Analyzer from Diapharma, also called the Whole-Blood Multiple Electrode Platelet Aggregometer (MEA)

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modular system for platelet aggregation and ristocetin cofactor testing.

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AggRAM from Helena

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Test cartridges contain membranes coated with

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collagen/epinephrine or collagen/ADP

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The Siemens PFA-100 Platelet Function Analyzer is an auto- mated instrument that provides rapid results on quantitative and qualitative platelet abnormalities. Test cartridges contain membranes coated with collagen/epinephrine or collagen/ADP to stimulate platelet aggregation.

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successful at detecting von Willebrand disease and the efficacy of aspirin therapy.

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PFA-100 system

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measures platelet aggregation by microbead agglutination.

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Verify Now from Accriva Diagnostics

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Test agent in verify now

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aspirin assay using arachidonic acid

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can measure multiple cellular activation-dependent changes related to platelet surface receptor upregulation and activation, generation of platelet microparticles, and binding of platelets to leukocytes, in addition to the traditional platelet secretion and aggregation markers

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Flow cytometry

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Molecular testing is now readily available for gene mutations of

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factor V (FV Leiden) prothrombin (prothrombin G20210A)

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accurate for the detection of both point mutations and single-nucleotide polymorphisms.

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PCR