Laboratory Evaluation of Platelets (F) Flashcards
What is the purpose of quantitative evaluation of PLTs?
Measures the # of PLTs per uL of blood
What is the characteristic of quantitative evaluation of PLTs?
It should be performed first
What is the purpose of qualitative evaluation of PLTs?
Detects PLT structure abnormalities
?What are the characteristics of qualitative evaluation of PLTs?
1) Suspected if bleeding symptoms, specifically mucocutaneous bleeding, are present
2) Suspected if PLT ct is > 50,000/uL
What is the purpose of PLT estimate?
Verifies the accuracy of released PLT cts from automated machines and obtained PLT cts from manual methods
How is PLT estimate performed?
Performed by using an EDTA whole blood in making a Wright-stained peripheral blood film and counting the # of PLTs seen in 10 OIFs
What is PLT ct?
It is the # of PLTs in 1 L or 1 uL of peripheral whole blood
How is PLT ct performed?
It is performed by adding diluting fluid to a small amt of EDTA whole blood and counting the approx # of PLTs seen in 25 small squares in the central large square of the hemocytometer
What is the normal range (in conventional unit) of PLT ct?
150,000 - 400,000/uL
What is the normal range (in SI unit) of PLT ct?
150 - 400 X 10^9/L
What is thrombocytosis?
Increased / high PLT ct
What is thrombocytopenia?
Decreased / low PLT ct
What is the purpose of PLT morphology in blood film?
It allows the evaluation of PLT appearance under the microscope
How is PLT morphology in blood film performed?
It is performed by using an EDTA whole blood in making a Wright-stained peripheral blood film and taking note of the size, granularity, clumping, and adherence to WBCs (neutrophils)
In PLT morphology in blood film, what is the only parameter that can be correlated w/ automated machine cts?
PLT size
Increased / high PLT ct = increased / high mean platelet volume
What are the diff PLT morphologies present in blood film?
1) Gray PLTs
2) Giant PLTs
3) Stress PLTs
4) PLT clumps
5) PLT satellitosis
6) Adherence to WBC
How is bleeding time performed?
It is performed by counting the duration of bleeding from skin puncture, assessing it at 30 sec interval, and reporting the result in minutes and seconds
When is bleeding time assessed?
For every 30 secs interval
What is the manner (or units) of reporting of bleeding time?
In minutes and seconds
What are the purposes of bleeding time?
1) It evaluates primary hemostasis specifically the PLT function
2) It is used to predict surgical bleeding
At what procedure bleeding time is first described and at what procedure is it modified?
First described by Duke; modified by Ivy
What is the characteristic of bleeding time?
It is now considered as an obsolete test due to intracapillary pressure, skin thickness, size of wound, and depth of wound
What is the normal range of bleeding time?
2 - 4 mins
What is the relationship bet bleeding time and PLT function?
Increased / prolonged bleeding time = decreased / low PLT function
What is the relationship bet bleeding time and blood vessel integrity?
Increased / prolonged bleeding time = decreased / low blood vessel integrity
What is the purpose of PLT aggregometry?
It evaluates PLT aggregation and PLT secretion using citrated PLT-rich plasma or citrated whole blood
How can PLT aggregometry be performed?
It can be performed using various methods:
1) Lumiaggregometry
2) Conventional PLT aggregometry
What are the diff PLT agonists?
1) Thrombin
2) ADP
3) Ristocetin
4) Collagen
5) Arachidonic acid
6) Epinephrine
What are the actions of thrombin?
1) It cleaves protease activatable receptors or PARs, GP Ib, and GP V
2) It also triggers secondary hemostasis within the sx; synthetic thrombin is reco (thrombin receptor-activating peptide)
What is the characteristic of thrombin?
It is the 1st agonist added because of its capability to induce full secretion
What is the action of ADP?
It binds P2Y1 and P2Y12 receptor
What is the characteristic of ADP?
It is most commonly used agonist for conventional aggregometry
What is the action of ristocetin?
It binds GP Ib/IX/V associated with VWF
What is the action of collagen?
It binds GP Ia/IIa and GP VI
What is the action arachidonic acid?
It is involved in eicosanoid pathway
What is the action of epinephrine?
It binds alpha(sign)-adrenergic receptors
What is the characteristic of epinephrine?
It cannot be used electrical impedance aggregometry
How is lumiaggregometry performed?
It is performed by adding an agonist to whole blood diluted w/ saline or citrated PLT-rich plasma to measure the aggregation reported in ohms and ATP secretion in nM
What should be done if PLT ct is < 100,000/uL in lumiaggregometry?
Whole blood sx should not be diluted w/ saline
What is the principle followed by lumiaggregometry?
It follows the principle of chemiluminescence that uses a firefly-derived luciferin-luciferase rgnt and the result is detected by a photodetector
What is the relationship bet luminescence and PLT aggregation?
Increased / high luminescence = increased / high PLT aggregation
What is the relationship bet luminescence and ATP secretion?
Increased / high luminescence = increased / high ATP secretion
What is the procedure (or steps) for PLT aggregation?
1) 300 - 500 of diluted WB or 500 uL PRP into the cuvette
2) Add 2 - 5 uL agonist directly to the cuvette
3) Add luciferin-luciferase
What is the procedure (or steps) for ATP secretion?
1) 300 - 500 of diluted WB or 500 uL PRP into the cuvette
2) Add ATP std directly to the cuvette
3) Add luciferin-luciferase
How is PRP conventional aggregometry performed?
It is performed by adding an agonist to citrated PLT-rich plasma to measure the aggregation reported in ohms
What is the principle followed by PRP conventional aggregometry?
It follows the principle of light transmittance and the result is detected by a photodetector
What happens in PRP conventional aggregometry?
More light passes as PLTs continue to aggregate
When is PRP conventional aggregometry not performed?
It cannot be performed if PLT ct is < 100,000/uL
What is the relationship bet light transmittance and PLT aggregation?
Increased / high light transmittance = increased / high PLT aggregation
What is the process (or steps) of PRP conventional aggregometry?
1) 300 - 500 uL of PRP into the cuvette
2) Drop 1 clean plastic stir bar into the cuvette
3) Place cuvette in incubation well
4) Incubate at 37 DC for 5 mins
5) Place cuvette in reaction well
6) Add an agonist directly to the cuvette
7) Turn on the light source
How is WB conventional aggregometry performed?
It is performed by adding an agonist to whole blood diluted w/ saline to measure the aggregation reported in ohms
What should be done if PLT ct is < 100,000/uL (in WB conventional aggregometry)?
If PLT ct is < 100,000/uL, whole blood sx should not be diluted w/ saline
What is the principle followed by WB conventional aggregometry?
It follows the principle of electrical impedance that uses low-voltage cartridge-mounted disposable direct current electrodes and the result is detected by instrument circuitry
What happens in WB conventional aggregometry?
PLTs coat the electrodes as they continue to aggregate
What is the relationship bet electrical impedance and PLT aggregation in WB conventional aggregometry?
Increased / high electrical impedance = increased / high PLT aggregation
What is the process (or steps) of WB conventional aggregometry?
1) 300 - 500 uL of diluted WB into the cuvette
2) Drop 1 clean plastic stir bar into the cuvette
3) Place cuvette in incubation well
4) Incubate at 37 DC for 5 mins
5) Place cuvette in reaction well
6) Add an agonist directly to the cuvette
7) Suspend a pair of electrode into the cuvette
What is the disorder that only has normal ristocetin?
only ristocetin normal = Glanzmann thrombasthenia
What are the actions (lab results) of the GP IIb/IIIa targeting drugs (in GT)?
1) PLT aggregation response to ADP: absent
2) PLT aggregation response to collagen: absent
3) PLT aggregation response to epinephrine: absent
4) PLT aggregation response to ristocetin: normal
5) PLT aggregation response to thrombin: absent
6) PLT aggregation response to arachidonic acid: absent
What are the disorders that has ristocetin as absent and thrombin as decreased?
1) Bernard-Soulier Syndrome
2) Von Willebrand Disease
What are the lab results for BSS and VWD?
1) PLT aggregation response to ADP: normal
2) PLT aggregation response to collagen: normal
3) PLT aggregation response to epinephrine: normal
4) PLT aggregation response to ristocetin: absent
5) PLT aggregation response to thrombin: decreased
6) PLT aggregation response to arachidonic acid: normal
?What is the meaning if collagen is absent?
X collagen = X GP Ia/IIa and GP VI receptor
?What is the meaning if ADP is decreased?
decreased / low ADP = X P2Y12 receptor and P2Y12-targeting drugs
?What is the meaning if epinephrine is decreased?
Decreased / low epinephrine = X alpha(sign)-adrenergic receptor
?What is the meaning if thrombin is decreased?
Decreased / low thrombin = X PAR and PAR-targeting drugs
?What is the meaning if arachidonic acid is decreased?
Decreased / low arachidonic acid = X enzymes of eicosanoid pathway
?What is the meaning if ADP, collagen, and epinephrine are all decreased?
Decreased / low ADP, collagen, epinephrine = storage pool disorders
?What is the meaning if collagen and arachidonic acid are absent?
X collagen, arachidonic acid = COX-targeting and NSAID
What are the diff PLT activation markers?
1) PF4 immunoassay
2) 11-Dehydrothromboxane B2 assay
What is the relationship bet plasma PF4 and PLT activation (in PF4 immunoassay)?
Increased / high plasma PF4 = increased / high PLT activation
How is PF4 immunoassay performed?
It is performed by adding small amt of plasma from CTAD whole blood in a microplate
What is the principle followed by PF4 immunoassay?
It follows the principle of ELISA that uses rgnt Abs to measure the concentration of the target Ag w/c is PF4
Elevated plasma PF4 is usually associated w/ what?
It is usually associated w/ thrombotic stroke or coronary thrombosis
What is the relationship bet 11-dehydrothromboxane B2 and PLT activation?
Increased / high 11-dehydrothromboxane B2 = increased / high PLT activation
How is 11-dehydrothromboxane B2 assay performed?
It is performed by adding small amt of random urine in a microplate
What is the principle followed by 11-dehydrothromboxane B2 assay?
It follows the principle of ELISA that uses rgnt Abs to measure the concentration of the target Ag w/c is 11-dehydrothromboxane B2
What is the characteristic of 11-dehydrothromboxane B2 assay?
Thromboxane A2 -> after 30 secs, thromboxane B2 -> w/ liver enzymes, 11-dehydrothromboxane B2
What is associated w/ elevated 11-dehydrothromboxane B2?
It is associated w/ aspirin failure
