LEC 6 0 HEMOSTASIS LABORATORY TESTING Flashcards
Most hemostasis procedures are performed on what type of specimen
platelet-poor plasma (PPP, plasma whose platelet count is less than
10,000/uL)
At the moment of collection, blood is mixed
with sodium citrate anticoagulant and is maintained as well
mixed whole blood for assays that require whole blood such as
platelet function tests
centrifuging mixed blood to produce platelet-rich plasma (plt count is approx 200,000/ul) is used in what assays
light transmittance platelet aggregometry
platelet-poor-plasma is used in what assays
clot based assays/coagulation studies
before performing blood collection, the clinician must ask about the clotting and bleeding history, as well as the blood group O people.
What is the significance of asking blood group O people for their blood type?
(group O people have a higher von Willebrand disease prevalence)
Bleeding and clotting characteristics come next, including ________, and whether events are
spontaneous or follow an injury or a surgical or dental proce
dure.
location, frequency, volume
aside from assessing their bleeding history, conditions, as well as the bleeding characteristics, what comes next to assess?
2-week drug history
assessing the 2-week drug history includes ______
anticoagulants (blood thinners)
antiplatelet drugs aspirin and non-steroidal anti-inflammatory drugs)
contraceptives
hormone replacement therapy (thrombotic)
The patient is also asked about over
the-counter remedies and dietary supplements, such as ______
ginger
garlic
vitamin K
St. John’s wort
If the patient is taking over
the-counter remedies and dietary supplements, it is instructed to discontinue at least how many days or weeks prior to blood collection
7 days or 1 week
Lastly, the clinician examines the patient for evidence of bleeding; ___ and ____
bruises and swelling
_______ may be employed to enhance bleeding history accuracy
Standardized bleeding assessment tools (BAT)
Patients need only fast under arranged circumstances
but are advised to avoid caffeine and exercise for ______
2 hrs
Patients need only fast under arranged circumstances
but are advised to avoid caffeine and exercise for 2 hours and
smoking for ________ before collection.
30 minutes
Patients need only fast under arranged circumstances
but are advised to avoid caffeine and exercise for 2 hours and
smoking for 30 minutes before collection. Patients should be
inactive for _______ before collection.
5 minutes
if there a reason to anticipate excessive bleeding - for instance, if the patient has multiple bruises , mentions a tendency to bleed, and possesses high BAT score - we must monitor the venipuncture site from the usual 1 mn to how many minutes before we dismissed the patient
5 mns
In the case of small, scarred, or fragile veins, the collector may fit a _____
needle infusion tube to a syringe, which enables the collector to
reduce and control the negative collection pressure.
23-gauge Luer-adapter needle or 23-gauge “butterfly”
Adult with good veins, collecting not more than 25 ml of blood is preferred to be collected using what needle gauge
20 or 21 needle gauge, thin walled, 1.0 or 1.25 inches long
Adult with good veins, collecting more than 25 ml of blood is preferred to be collected using what needle gauge
19 gauge needle
child or adult with small fragile or hardened veins are preferred to be collected using what gauge of needle
23 gauge, winged needle set; collect with small evacuated tubes or syringe
the transferring of blood from syringe to tube is done using
19 gauge safety transfer unit; slowly inject through tube closure
Most hemostasis specimens are collected in plastic blue-closure (blue-top, blue-stopper) sterile evacuated blood collection
tubes containing a measured volume of buffered ______
anticoagulant.
sodium citrate
what type of tube for collecting blood is suitable but its use is declining due to possible breakage and consequent risk of exposure to bloodborne pathogens
Siliconized (plastic-coated) glass tubes
are Tubes of uncoated soda-lime glass unsuitable for collection?
no po
content and percent of sodium citrate used
0.105 - 0.109 M (3.2%) sodium citrate
why sodium citrate is the best anticoagulant for most hemostasis testin?
sodium citrate binds calcium ions to prevent coagulation and the buffer stabilizes the specimen pH as long as the tube closure remains in place
Upon collection, the anticoagulant solution mixes with blood to produce what ratio
9:1 ratio
the collection ratio of 9:1 has what legends
9 parts whole blood to 1 part
anticoagulant
In most cases, 0.3 mL of anticoagulant mixes
with _______ mL of whole blood
2.7
The ratio yields a final citrate concentration of _______ of anti
coagulant in whole blood
10.5 to 10.9 mM
The 9:1 blood-to-anticoagulant ratio is effective, provided the
patient’s hematocrit is _______
55% or below
formula for computing sodium citrate anticoagulant in patients who have hct of 55% and above
C = (1.85 10^-3 ) (100 - HCT) V
do we need to increase the anticoagulant for specimens from patients with anemia, even when the hematocrit is less than 20%?
no, there is no existing evidence suggesting a need for increasing the volume of sodium citrate
why do practitioners do not use ethylenediaminetetraacetic acid for coagulation testing?
EDTA irreversibly chelates calcium ions
EDTA doesn’t preserve labile factors
inhibits thrombin-fibrinogen reaction
calcium ion chelation with citrate is can be reversed with the addition of
calcium chloride
If EDTA is not used for coagulation test, what can we use it for?
complete blood count including PLATELET COUNT
________ (anticoagulant) specimens have never been validated for plasma
coagulation testing but may be necessary to produce accurate
platelet counts in cases of PLATELET SATELLITISM (satellitism) as a
substitute for specimens collected in EDTA.
Heparinized (green closure)
reason why we are not using heparin for hemostasis testing?
binds with anti-thrombin III
inhibits all coagulation reaction
if heparin is not for coagulation testing, what are the assay or test we can use heparin?
platelet retention/glass bead retention test
aside from platelet count, what is the use of EDTA in hemostasis testing?
EDTA may be required for specimens used for molecular diagnostic testing, such as testing for the FACTOR V LEIDEN MUTATION.
tubes used for molecular diagnostic such, as specified by institutional protocol
acid citrate dextrose (ACD, yellow closure) and dipotassium EDTA (K2EDTA, white closure
anticoagulant in yellow closure
acid citrate dextrose (ACD)
dipotassium EDTA (k2EDTA ) is an anticoagulant in what closure
dipotassium EDTA (k2EDTA )
tubes suppress in vitro platelet or coagulation activation for specialty assay
Citrate theophylline adenosine dipyridamole (CTAD, blue closure)
what is the in vitro platelet or coagulation activation specialty assay that Citrate theophylline adenosine dipyridamole (CTAD, blue closure) is used for?
platelet activation marker platelet factor 4 (PF4)
or
coagulation activation marker thrombin-antithrombin complex (TAT)
Nonadditive tubes include _____ (but not plastic) tubes and clear
closure plastic tube
red-closure glass
what should we do if w non additive tubes are unavailable?
the phlebotomist may use and discard a preliminary blue-closure
tube when following an additive tub
this venipuncture procedure is Preferred over syringe method
evacuated tube system
this venipuncture procedure allows the Blood directly mixes with anticoagulant
evacuated tube system
ORDER OF DRAW
oRed top tube
oLight blue
oEDTA
oPlastic syringe
in Syringe Method
what is the use of first syringe
sample collected is discarded
or
can be used for other serological test
in syringe method, what is the use of 2nd syringe
collected for coagulation studies
2 reasons why we need to discard the first syringe in 2-syringe method
prevent contamination
maintains accurate result
what type of pressure is in evacuated tube that allows to collect correct volume of blood
negative internal pressure
why do we need to prevent having shortdraw in coagulation testing
generates erroneously PROLONGED clot-based coagulation test results because the excess anticoagulant neutralizes test reagent calcium
what should we do in short draw specimen
Short-draw specimens are discarded, and
a fresh specimen is collected.
Evacuated tubes are designed so that the _____
pressure collects the correct volume of
negative internal
. In most cases the volume of blood collected
must be within ________% of the calibrated volume
90
how does the phlebotomist compensates for the internal volume of the tubing using butterfly winged set
by collecting and discarding a non additive tube or a blue closure tube. This step ensures that the needle set tubing is filled with fresh patient blood before the hemostasis specimen is collected and avoids an inadvertent short draw
Clotted specimens are useless for hemostasis testing, even if
the clot is small
true or false
true
how many invert we need right after mixing the blood to anticoagulant
at least 3 times
Excessive specimen agitation, called “_______,” causes hemolysis (RBC rupture), procoagulant activation, and platelet activation
cocktail shaking
During blood collection, the phlebotomist must remove the
tourniquet within 1 minute of its application to avoid ____, which
slows venous flow
stasis
_________ results in endothelial cell activation
and hemoconcentration with the local accumulation of coagulation factors V, VII, VIII, XII, and von Willebrand factor (VWF),
which may falsely shorten clot-based coagulation test results.
Stasis
collecting blood in vascular access device
Before blood is collected for hemostasis testing, the line must be
flushed with______ of saline,
5 mL
collecting blood in vascular access device
Before blood is collected for hemostasis Before blood is collected for hemostasis testing, the line must be
f lushed with 5 mL of saline, and the first ______ of blood, or six
times the volume of the blood collection tube, must be collected and discarded.
5 mL
example of vascular access device
IV catheter, cannula, heparin or saline locks, peripherally inserted central catheters, central venous catheters, dialysis catheters
site of capillary function
off center of the fingertip and perpendicular to the fingerprint lines
what type of blood is ideal for capillary puncture coagulation test
free flowing blood
Further, hemolysis interferes with _______ result
optical endpoint coagulometer
LIPEMIC OR ICTERUS SAMPLE interfere with __ method
chromogenic substrate
in a lipemic or icteric sample. The practitioner must employ an _________ instrument.
electro-mechanical detection method
Storage at REFRIGERATOR (1-6*c) temperatures causes _____
precipitation of large von Willebrand factor multimers,
activation of coagulation factor VII,
activation of platelets,
and destruction of platelet integrity.
Storage at above standard room temperature (>25*C) causes coagulation __ to deteriorate.
factors V and VIII
what will happen if the CO2 diffused due to unsealing the collection tube?
pH rise and results to falsely prolonged PT and PTT
relationship of pH to bleeding
rise in pH increase PT and PTT
alkaline blood means bleeding
Specimens are maintained at ambient temperature, ____, never at refrigerator temperatures or on ice
15° C to 25° C
Specimens collected for PTs may be held uncentrifuged or centrifuged at 15° C to 25° C and tested within ____ hours of the
time of collection
24
what pathway is related to PT?
PTEX
PT = EXTRINSIC PATHWAY (FIII and FVII)
what pathway is related to PTT?
intrinsic and common pathway
Specimens collected for PTTs and most
other clot-based assays are also held uncentrifuged or centri
fuged at 15° C to 25° C, but they must be tested within ___ hours
of time of collection.
4 hrs
If a patient is receiving unfractionated
heparin (UFH) therapy, PTT specimens must be centrifuged
within 1 hour of the time of collection to avoid depletion of the
________
heparin
Centrifuges that are used to prepare hemostasis specimens must maintain a temperature of __________
15° C to 25° C
If any plasma-based hemostasis assay cannot be completed
within the prescribed interval, the practitioner must centrifuge
the specimen within ________ hour of collection
1 hour
The practitioner immediately transfers the PLASMA by plastic pipette to a __
plastic freezer tube
are we allowed to use glass containers for plasma-based hemostasis upon separation of plasma
no, glass stimulates the intrinsic coagulation pathway
The freezer tube for plasma based hemostasis is stored at ____ for up to 2 weeks
-20*C
The freezer tube for plasma based hemostasis is stored at ____ for long term storage (6 months )
-70*C
PT with no UFH
specimen stability
test within 24 hr maintain upright and sealed
PTT with no UFH
specimen stability
test within 4 hr maintain upright and sealed
PTT with monitoring UFH
centrifuge to separate plasma within 1 hr, test within 4 hr
PT with monitoring UFH
centrifuge to separate plasma within 1 hr, test within 4 hr
factor assays specemin stability
test within 4 ht maintain upright and sealed
optical platelet aggregometry using PRP specimen stability
wait within 30mn after centrifugation and test within 4hr of collection
To avoid cryoprecipitation of VWF, specimens
may not be frozen and thawed more than once
true or false
true
Aggregometry should be started immediately and must be completed within ______ hours of specimen collection (for undiminished ex vivo platelet activity).
4
whole blood specimen for platelet aggregometry is collected at ___ in ___ temperature
3.2% sodium citrate and held at
15° C to 25° C until testing
Most specimens for whole-blood aggregometry are mixed
____ with normal saline before testing, although if the platelet count is less than 100,000/mL the specimen is
tested undiluted
1:1
___ are designed to test PRP (Platelet-Rich Plasma)
Light-transmittance (optical) platelet aggregometers
platelet poor plasma has how many platelets?
less than 10,000/ul or < 10 x 10^9 plt/L
centrifugation of PPP
10-15 mn, 2000 - 2500 rpm
PPP is tested within
2 hrs
refrigerated temp of PPP
no longer 4 hrs
freezing temp of PPP
-20 to -70*C
PPP is used in what studies
coagulation studies
Platelet Rich Plasma (PRP) has how many PLTS
250 x 10 ^9 PLT/l
CENTRIFUGATION of PRP
10-15 mns 60-100 rpm
PRP is stored at what temp
room temp
PRP is used in what studies
platelet studies
How aspirin affects hemostasis testing?
inhibits cyclooxygenase
in plt aggregation test, the patient must refrain taking aspirin prior the test for howmany days
7 days
for bleeding time, patients taking aspirin must refrain from taking it prior the collection for how many days
1 day
how heprarin affects hemostasis testing
affects cyclooxygenase
inhibits most clotting factors
antagonist of prothrombin group and vitamin K dependent clotting factors
warfarin/coumadin
it prevents gamma carboxylation of vitamin K on clotting factors
warfarin/coumadin
it alters blood vessels and induces hemolysis
penicillin
most potent penicillin capable of affecting platelet function
carbenicillin
it prematurely activates clotting process (extrinsic pathway )
tissue thromboplastin contamination
this factor is must be activated only when the reagent is added
tissue thromboplastin
a factor that affects the specimen and is associated with collagen for in vitro activation of clotting process
glass surfaces
the factors that prematurely activates at ref temp 4*C
factor VII and Factor XI
factors that deteriorates if left at room temp for extended period of time
labile factors factor V and factor VIII
how hemolysis affects sample and testing
releases tissue thromboplastin like substance that will activate clotting system
release ADP that causes platelet aggregation
how tourniquet affect hemostasis testing
causes venous stasis
activates clotting factors
increased pH effect to hemostasis testing
associated with loss of carbon dioxide that deteriorates clotting factors
sample must be unopened and tested within 6 hrs
effect of polycythemia vera in hemostasis testing
increases hematocrit by >50%
prolongs clotting time test
incomplete filling of tubes can result to ___
increased amount of citrate (prolonged)
