also known as clotting, is the process by
which blood changes from a liquid to a gel,
forming a blood clot. It potentially results
in hemostasis, the cessation of blood loss
from a damaged vessel, followed by repair.
The mechanism of coagulation involves
activation,
adhesion
and
aggregation
of platelets, as well as deposition and
maturation of fibrin
Whole blood :require to anticoagulant tube and
shaking , but no require to centrifuge.
Plasma : require to anticoagulant tube ,
shaking and centrifuge .
Serum: no require to anticoagulant tube and
shaking , but require to period clot and
centrifuge .
1- Ethylene Di amine Tetra Acetic Acid EDTA:
strongly and irreversibly binds calcium ions
preventing blood from clotting. Citrate is in
liquid form in the tube and is used
for
coagulation
tests,
as
well
as
in blood transfusion bags.
EDTA is the
most commonly used anticoagulant in the
hematology laboratory and is the anticoagulant
of choice for the CBC and HbA1c since it dose
not change the morphology , shape and
composition of blood cells.
the best concentration of EDTA is 1.2 mg
/1ml of blood Excess EDTA causes shrinkage
of RBC , causing falsely reduced hematocrit
(HCT),and subsequent increase in MCHC and
decrease in MCV .
2-Tri sodium citrate:
Is the anticoagulant of choice for
coagulation tests to prepare plasma for the
evaluation of coagulation disorders used in
platelet function tests also is used for ESR
(erythrocyte sedimentation rate tests ). It acts
by
precipitating calcium , it will not be
available for clotting process in these tests .
3-Double oxalate:
Consist of a mixture of (6parts ) of
ammonium oxalate and (4parts ) of
potassium oxalate.Double oxalate is no
longer used because it is rapidly caused
crenation of erythrocytes and distortion of
leukocytes on blood smears and because it is
toxic so, it cannot be used in blood donation
.
4-Sodium Fluoride :
This anticoagulant is used for preparing
blood specimens for the determination of
glucose and urea in plasma by non –
enzymatic methods because fluoride inhibits
glycolic enzymes and thereby prevents loss of
glucose during transportation or delay in
specimen handling.
5-Heparin:
Consider of essential constitutive blood, but
which blood film gave blue faints coloration
background when stain .this type are used for
plasma biochemistry tests .
Due
to
the
breakdown
of
red blood cells is important to the
laboratory because it can have an effect
on
laboratory
results.
In
general,
slight
hemolysis
has
little
effect
on most tests; however, it will cause
increased test results for specific tests like
potassium
and
lactate
dehydrogenase
because
it
can
have
an
effect
on laboratory results.
1-Mix tubes with anticoagulant additives
gently 5-10 times
2-Avoid drawing blood from a hematoma
3-Avoid drawing the plunger back too
forcefully, if using a needle and syringe, or
too small a needle.
4-Make sure the venipuncture site is dry
5-Avoid a probing, traumatic venipuncture
6-Avoid prolonged tourniquet application or
fist clenching.