2. WHAT IS COAGULATION?
â—ŹCoagulation is a complex process by which blood forms clots.
Blood must be remain fluid with in the vasculature and yet clot
quickly when expose to non endothelial surface at a site of
vascular injury.
â—ŹIt is an important part of haemostasis (the cessation of blood
loss from a damaged vessel), where in a damaged blood vessel
wall is covered by a platelet and fibrin-containing clot to stop
bleeding and begin repair of the damaged vessel.
â—ŹDisorders of coagulation can lead to an increased risk of
bleeding (hemorrhage) or clotting (thrombosis).
3. Hemostasis is maintained in the body via three
mechanisms:
â—ŹVascular spasm - Damaged blood vessels.
constrict
â—ŹPlatelet plug formation - Platelats adhere to
damaged endothelium to form platelet plug
(primary hemostasis) and then degranulate.
â—ŹBlood Coagulation - Clots form upon the
conversion of fibrinogen to Fibrin, and its
addition to the platelet plug (secondary
hemostasis).
4. Factor I Fibrinogen Factor VIII
Factor II Prothrombin Factor IX
Factor III Thromboplastin Factor X
Factor IV Calcium Factor XI
Factor V Factor XII
Antihemophilic
globulin
Partial
thromboplastin
component
Stuart-Prower
factor
Plasma
thromboplastin
antecedent
Hageman factor
Factor VII
Labile or
proaccelerin
Stable factor or
proconvertin
Factor XIII Fibrin-
stabilizing factor
19. Clotting Time - Slide Method
• The surface of the glass tube
This test
initiates the clotting process.
is sensitive to the
•
factors involved in the intrinsic
pathway
The expected range for clotting
time is 4-10 min.
21. PT
â—ŹThe prothrombin time: is the time
required for the plasma to clot after an
excess of thromboplastin and an optimal
concentration of calcium have been added.
â—ŹMeasures the function of the Extrinsic
Pathway.
â—ŹSensitive to Factors I, II, V, VII, X.
â—ŹThe PT evaluates patients suspected
of having an inherited or acquired
deficiency in these pathways.
23. When is it ordered?
â—ŹUsed to monitor oral anticoagulant therapy (Warfarin /
Coumadin).
â—ŹWhen a patient who is not taking anti-coagulant drugs
has signs or symptoms of a bleeding disorder.
â—ŹWhen a patient is to undergo an invasive medical
procedure, such as surgery, to ensure normal clotting
ability.
24. An elevated prothrombin time
may indicate the presence of:
Vitamin K deficiency
(Vitamin K is needed to make prothrombin and other clotting factors)
➢
➢
➢
DIC
liver disease
a deficiency in one or more of the following factors:
I, II, V, VII, X.
Anticoagulant (warfarin)
25. INR
â—ŹA PT test may also be called an INR test.
â—ŹINR (international normalized ratio) stands for a way of
standardizing the results of prothrombin time tests, no
matter the testing method.
â—ŹSo your doctor can understand results in the same way
even when they come from different labs and different
test methods.
â—ŹUsing the INR system, treatment with (anticoagulant
therapy) will be the same. In some labs, only the INR is
reported and the PT is not reported
26. â—ŹAn INR of 1.0 means that the patient PT is
normal.
â—ŹAn INR greater than 1.0 means the
clotting time is elevated.
â—ŹINR of greater than 5 or 5.5 = unacceptable
high risk of bleeding,whereas if the INR=0.5
then there is a high chance of having a clot.
●Normal range for a healthy person is 0.9–1.3,
and for people on warfarin therapy, 2.0–3.0,
although the target INR may be higher in
particular situations, such as for those with a
mechanical heart valve.
28. PTT
â—ŹThe partial thromboplastin time (PTT) or activated partial
thromboplastin time (aPTT or APTT( is a performance
indicator measuring the efficacy of both the "intrinsic" and
the common coagulation pathways.
â—ŹIt is also used to monitor the treatment effects with
heparin a major anticoagulant.
â—ŹKaolin cephalin clotting time (KccT) is a historic name for
the activated partial thromboplastin time
30. â—ŹNormal PTT times require the presence of the
following coagulation factors:
I, II, III, IV, V, VI, VIII, IX, X, XI, & XII
31. When is it ordered?
â—ŹWhen a patient presents with unexplained bleeding or
bruising,
â—ŹIt may be ordered as part of a pre-surgical evaluation for
bleeding tendencies,
â—ŹWhen a patient is on intravenous (IV) or injection heparin
therapy, the APTT is ordered at regular intervals to
monitor the degree of anticoagulation.
32. Prolonged APTT may indicate:
â—ŹUse of heparin.
â—Źantiphospholipid antibody:especially lupus anticoagulant,
which paradoxically increases propensity to thrombosis
â—Źcoagulation factor deficiency ,
e.g hemophilia
â—ŹDIC
â—ŹLiver disease
33.
34. FACTOR DEFICIENCIES
âť– Inherited:
1. HEMOPHILIA A
2. HEMOPHILIA B
3. VON
WILLEBRAND’S
DISEASE
âť– Acquired:
1. Anticoagulant
therapy
2. Liver diseases
3. DIC
35. HEMOPHILIA A (Classic Hemophilia)
â—Ź 80-85% of all Hemophiliacs
â—Ź Deficiency of Factor VIII
â—Ź Lab Results - Prolonged PTT
36. â—ŹHEMOPHILIA B (Christmas Disease)
â—Ź 10-15% of all Hemophiliacs
â—Ź Deficiency of Factor IX
â—Ź Lab Test - Prolonged PTT
37. ●VON WILLEBRAND’S DISEASE
â—Ź Deficiency of VWF & amount of Factor VIII
â—Ź Factor VIII is bound to vWF while inactive in circulation;
Factor VIII degrades rapidly when not bound to vWF
â—Ź Lab Results - Prolonged BT, PTT
38. ANTICOAGULANTS
â—Ź An anticoagulant is a substance that prevents
coagulation; that is, it stops blood from clotting
â—Ź This prevents deep vein thrombosis,
pulmonary embolism, myocardial infarction
and stroke.
ANTICOAGULANTS
1. Coumadins (Vitamin K antagonists)
2. Heparin
39. Coumadin's
â—ŹThese oral anticoagulants that antagonize the effects of
vitamin K.
â—ŹExamples include warfarin. It takes at least 48 to 72 hours
for the anticoagulant effect to develop. Where an
immediate effect is required, heparin must be given
concomitantly.
â—ŹMonitored by PT times
â—ŹThese anticoagulants are used to treat patients with deep-
vein thrombosis (DVT), pulmonary embolism (PE), atrial
fibrillation (AF), and mechanical prosthetic heart valves.
40. Heparin
â—ŹHeparin is a biological substance.
â—ŹIt works by activating antithrombin III,
which blocks thrombin from clotting
blood.
â—ŹHeparin Therapy is Monitored by PTT times
â—ŹLow molecular weight heparin is a more
highly processed product that is useful as it
does not require monitoring of the APTT
coagulation parameter (it has more
predictable plasma levels) and has fewer side
effects.
42. DIC
â—ŹDisseminated intravascular coagulation
(DIC is a pathological activation of
coagulation) blood clotting mechanisms
that happens in response to a variety of
diseases
â—ŹDIC leads to the formation of small blood
clots inside the blood vessels throughout the
body
â—ŹThe small clots also disrupt normal blood
flow to organs (such as the kidneys), which
may malfunction as a result
43. â—ŹAs the small clots consume coagulation
proteins and platelets, normal coagulation is
disrupted and abnormal bleeding occurs from
the skin the gastrointestinal tract, the
respiratory tract and surgical wounds.
â—ŹThe PT and APTT are usually very
prolonged and the fibrinogen level
markedly reduced
â—ŹHigh levels of fibrin degradation products,
including D- dimer, are found owing to the
intense fibrinolytic activity stimulated by the
presence of fibrin in the circulation.
44. Definitive diagnosis depends on the result
of DIC:
â—ŹThrombocytopenia (prolonged bleeding
time)
â—ŹProlongation of prothrombin time and
activated partial thromboplastin time
â—ŹA low fibrinogen concentration
â—ŹIncreased levels of fibrin degradation
products
45. Pre-analytic errors
â—ŹProblems with blue-top tube
â—Ź Partial fill tubes
â—Ź Vacuum leak and citrate
evaporation
â—ŹProblems with phlebotomy
â—Ź Heparin contamination
â—Ź Wrong label
â—Ź Slow fill
â—Ź Underfill
â—Ź Vigorous shaking
â–
Biological effects
•
•
Hct ≥55 or ≤15
Lipemia,
hyperbilirubinemia,
hemolysis
â–
Laboratory errors
•
•
•
Delay in testing
Prolonged incubation at 37°C
Freeze/thaw deterioration