Coagulation Instrumentation Flashcards
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
Tilt-tube technique
The 1950s witnessed the dawn of the modern era of instru- mentation in coagulation testing with the development of the first coagulometer
BBL Fibrometer.
Subsequent 20th century developments in clot detectors in- cluded a
rolling steel ball and photo-optical measurements
Coagulation instruments apply clot detection principles that either
observe” the clot formation (optical and nephelometric devices)
detect the clot by “feel” (mechanical and viscosity- based devices).
detect a change in plasma optical density (OD; light transmittance) during the clotting process.
Photo-optical (turbidometric) coagulometers
Principle of photo optical
LIGHT TRANSMITTANCE
used to detect clot formation in the past is still used today in particular instruments for whole blood clotting.
viscoelastic technique
vital for assesing hemostasis
viscoelastic technique
Chromogenic (synthetic substrate, amidolytic) methodology uses a synthetic small peptide substrate conjugated to a chromo- phore, usually
para-nitroaniline (pNA).
means for measuring the activity of a specific coagulation fac- tor because it exploits the factor’s enzymatic (protease) proper- ties.
Chromogenic analysis
The activity of coagulation enzymes is measured by
direct or indirect chromogenic methods
a modification of photo-optical end-point detection in which 90-degree or forward-angle light scatter, rather than OD, is measured.
Nephelometry
and a photodetector detects variations in
light scatter at 90 degrees (side scatter)
180 degrees (forward-angle scatter)
be adapted to measure the dynamics or kinetics of clot formation.
Nephelometry
are the newest assays available for routine coagulation testing.
Immunologic assays
ASSAY END-POINT DETECTION PRINCIPLES
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
Tradi- tionally, PT assays required. (Reagent and specimen volume)
100 ul of patient plasma and 200 uL of thromboplastin/calcium chloride reagent
flexibility of selecting reagents that best suit their needs, and prefer not to be restricted in their choicesby the analyzer being used.
Open Reagent Systems
has improved the safety and efficiency of coagulation testing.
Closed-tube sampling of specimens
premature activation of coagulation factors and platelets
that generate FVIIa and thrombin.
Clotted
OD-sensing instruments because of interference with light
transmittance.
Lipemia
Hemolysis
Causes falsely shortened
Clotted
Hemolysis
Falsely prolonged
Icterus
Lipemia
Falsely elevated
Abnormal clot formation
A second common POC test is the
prothrombin time/ international normalized ratio (PT/INR) f
technique uses the viscoelastic property of blood clotting
Thromboelastography
The assay pro- vides information on the entire kinetic process of whole blood clot formation.
Thromboelastography
Clot initiation or clotting time
TEG- R
ROTEM- CT
Comment- Time of initial fibrin formation
Clot kinetics
TEG- K
ROTEM- CFT (clot formation time)
COMMENT- measure of the speed to reach a specific level of clot strength
📐
TEG- a
ROTEM- a
COMMENT- Measure of the rate of clot formation, reflects the rate of fibrin formation and cross linking
Clot strength
TEG- MA (maximum amplitutde)
ROTEM- MCF (maximum clot firmness
COMMENT- Measure of the strength of the clot
Clot stability
TEG- Ly30 (lysis at 30 minutes as a ratio of MA)
ROTEM- CLI (clot lysis index)
COMMENT- Measure of the rate of amplitude reduction
Platelet Aggregometers principle
Light transmittance
This test system measures the increase in light transmission that occurs in direct propor- tion to platelet aggregation
Platelet Aggregometers
mea- suring the platelet secretion response using the luciferase reagent
Chrono-Log has a Whole Blood/Optical Lumi-Aggregation
Chronolog principle
Electrical impedance
used to detect aggregation, and optical density to detect luminescence identifies platelet secretion.
Electrical impedance
monitors platelet function by impedance, is the latest development.2
Multiplate Analyzer from Diapharma, also called the Whole-Blood Multiple Electrode Platelet Aggregometer (MEA)
modular system for platelet aggregation and ristocetin cofactor testing.
AggRAM from Helena
Test cartridges contain membranes coated with
collagen/epinephrine or collagen/ADP
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.
successful at detecting von Willebrand disease and the efficacy of aspirin therapy.
PFA-100 system
measures platelet aggregation by microbead agglutination.
Verify Now from Accriva Diagnostics
Test agent in verify now
aspirin assay using arachidonic acid
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
Flow cytometry
Molecular testing is now readily available for gene mutations of
factor V (FV Leiden)
prothrombin (prothrombin G20210A)
accurate for the detection of both point mutations and single-nucleotide polymorphisms.
PCR
