Transcript Mixing studies

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Vidu Bala Mokkala.
 Sohail Chaudhry.
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59 year old female was seen by the PCP for pre-op evaluation
for septoplasty and was found to have incidental abnormal
PTT and was referred to the hematology and oncology clinic
for further evaluation.
PMH- HTN, Dyslipidemia, DM, Mild depression, Anxiety
disorder.
PSH: Appendectomy, Cholecystectomy, Partial Hysterectomy
for heavy menstrual cycles 30 yrs back.
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SH: Never smoked. Not an alcoholic.
FH: No bleeding disorders in the family.
Home medications: Metformin,Januvia,Gemfibrozil,
Zetia,Crestor,MVT,Lotrel,Atenolol,Lexapro,Calcium
and Vitamin D, Aspirin,Omeprazole.
Vitals: Stable.
Physical examination-Negative.
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CBC- WBC-5.7, HGB-11.6,HCT-36.1,PLT339.
CMP-Normal.
PT/INR-Normal.
PTT-66.7.(Increased)
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Coagulation is a complex process by which blood forms clots.
Disorders of coagulation can lead to an increased risk of
bleeding(hemorrhage) or clotting(thrombosis).
Hemostasis is the process of blood clot formation at the site of
vessel injury.
Platelets immediately form a plug at the site of injury and this
primary hemostasis.
Secondary hemostasis occur simultaneously: proteins in the blood
plasma, called coagulation factors or clotting factors, respond in a
complex cascade to form fibrin strands which strengthen the
platelet plug.
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Platelet Activation-collagen and thrombin.
Platelet Adhesion-platelet glycoprotein Ib-IX-V complex binding to the VWF
in the subendothelial matrix.
Platelet Aggregation- via fibrinogen receptors/Glycoprotein IIB-IIIA
receptors.
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Platelet Secretion(Granules)-alpha and dense granules.
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Fibrin plug formation.
1.Cyclooxygenase inhibitors: Aspirin
2.Adenosine diphosphate (ADP) receptor inhibitors
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Clopidogrel (Plavix)
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Ticlopidine (Ticlid)
3.Phosphodiesterase inhibitors: Cilostazol(Pletal
4.Glycoprotein IIB/IIIA inhibitors (intravenous use only)
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Abciximab (ReoPro)
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Eptifibatide (Integrilin)
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Tirofiban (Aggrastat)
5.Adenosine reuptake inhibitors: Dipyridamole (Persantine)
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Vitamin K antagonists(Coumadin): Inhibits the vitamin K-dependent synthesis of
biologically active forms of the calcium-dependent clotting factors II, VII, IX and
X, as well as the regulatory factors protein C, protein S.
Unfractionated Heparin(UFH): Binds to Antithrombin(AT) at the site of native
pentasaccharide sequence, changing its conformation and converting it from
slow to a rapid inactivator of several coagulation factors, particularly X a. In
order to inactivate thrombin,heparin should bind to thrombin and AT
simultaneously,an effect that occurs only when the molecule exceeds 18
monosaccharide units (greater than 6000 daltons).
Direct thrombin inhibitors(DTI): Univalent DTI'S (Argatroban and dabigatran) and
Divalent DTI'S (Hirudin,Lepirudin,Bivalirudin).
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Low Molecular Weight Heparin (ardeparin,certoparin,enoxaparin,nadroparin,
reviparin,dalteparin, tinzaparin,parnaparin): Similar action as UFH. They have
lesser effect on thrombin than Xa because most of the molecules are not long
enough to bind simultaneously with thrombin and AT.
Synthetic pentasaccharide inhibitors of factor Xa (Fondaparinux and
Idraparinux): synthetic sugar composed of the five sugars (pentasaccharide) in
heparin that bind to antithrombin. It is a smaller molecule than low molecular
weight heparin.
Etiology for prolonged PT with normal PTT:
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Inherited: Factor VII defeciency.
Acquired:
Acquired factor VII deficiency
Vitamin K deficiency- biliary obstruction, malabsorption, cystic fibrosis,
resection of the small intestine,Certain antibiotics (particularly some
cephalosporins and other broad-spectrum antibiotics), salicylates,
megadoses of vitamin E, and hepatic insufficiency, coumadin.
Liver disease
Coumadin administration
Inhibitor of factor VII.
Etiology for prolonged PTT with normal PT:
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Inherited
Deficiency of factors VIII, IX, or XI
Deficiency of factor XII, prekallikrein, or HMW kininogen-Not associated with
a bleeding diathesis.
von Willebrand disease
Acquired
Heparin administration
Inhibitor of factors VIII, IX, XI, or XII
Acquired von Willebrand disease
Lupus anticoagulant-associated with thrombosis, rather than bleeding
Etiology of elevated PTT and PT:
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Inherited
Deficiency of prothrombin, fibrinogen or factors V or X
Combined factor deficiencies
Acquired
Liver disease
Disseminated intravascular coagulation
Supratherapeutic doses of heparin
Supratherapeutic doses of coumadin
Combined heparin and coumadin administration
Combined argatoban and coumadin administration
Inhibitor of prothrombin, fibrinogen or factors V or X
Primary amyloidosis-associated factor X deficiency
APTT -83.0 (22.3-37.8)
2. APTT 1:1 mixing studies-46.2 (22.3-37.8)
3. BT-3.5 (2.3-9.5)
4. Factor XII activity-140 (50-150)
5. Factor XI activity -175 (65-150)
6. Factor IX activity -188 (60-166)
7. Factor VIII activity-221 (50-180),inhibitor negative
8. Factor V activity -152 (>50 IU/DL),inhibitors are not tested when activity of
Factor V is (>50 IU/DL)
9. Lupus anticoagulant- undected.
10. Cardiolipin Ab. -negative (IGG and IGM-<10)
11. Platelet Function Studies:Collagen/Epinephrine closure time-107.
12. Beta 2 glycoprotein antibody –negtive.
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13. VWF
comprehensive screen-Negative.
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an abnormality in a clotting test (PT/PTT)has been detected, it
is important to differentiate between a clotting factor deficiency and
an inhibitor (an antibody or other interfering substance directed
against the clotting factor).
There are three important principles underlying such mixing tests:
•As
a general rule, clotting tests will give normal values when 50
percent activity of the involved coagulation factors are present.
Thus, if the clotting test returns to normal after a 1:1 dilution with
normal pooled plasma, a factor deficiency was the cause of the
abnormal test.
•Most
agents which inhibit clotting factor activity (such as
antibodies) will not be effectively diluted out after addition of an
equal volume of normal pooled plasma. Thus, if the test remains
abnormal after 1:1 dilution, an inhibitor was the cause of the
abnormal test.
•Some
inhibitors may give normal results when tested immediately
after 1:1 dilution; incubation of the diluted sample for up to two
hours at 37ºC may resolve this issue. As an example, delayed
reactivity is characteristic of factor VIII inhibitors.
•If
the 1:1 dilution corrects the abnormal test, the deficient factor(s)
can be determined by individual clotting factor assays.
If the test is not corrected by dilution, the most common inhibiting factors are:
•Heparin in the sample
•Antiphospholipid antibodies; these are more commonly associated with a
hypercoagulable state rather than bleeding.
•Inhibitors directed against factors VIII, IX, or X. These inhibitors can be associated
with life-threatening bleeding and require urgent attention by a hematologist and the
involved laboratory. Inhibitors of thrombin, such as fibrin or fibrinogen degradation
products. These can be detected using a variety of assays (such as fibrin degradation
products or D-dimer).
•Inhibitors to other factors. These are less common and are detected by individual
factor assays.
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A first step in evaluating an isolated prolonged aPTT or TT is to
exclude heparin as the etiology. This is especially important in
hospitalized patients, in whom blood is often drawn from
heparinized venous access devices.
The simplest approach is to redraw a blood sample using an
uncontaminated peripheral vein. Alternatively, one can use one of
the following two methods:
Reptilase time method: perform a thrombin time (TT) and reptilase
time (RT). Heparin is present if the TT is prolonged and the RT is
normal. Reptilase, a thrombin-like enzyme obtained from snake
venom, differs from thrombin by resisting inhibition by heparin via
antithrombin III.
Heparin reversal method: if a prolonged TT is normalized after the
addition of protamine a commercially available ion exchange resin
which absorbs heparin in the sample (Heparsorb), or a heparinase
(Hepzyme), heparin or a heparin-like material is present.