Laboratory Studies of Hemostasis - Wong Flashcards
What is INR used for
concentration of warfarin - anticoagulant therapy
What would an anti-Xa test be used for?
heparin concentration
sodium citrate tube
blue top tube
- anticoagulant
What are causes of prolonged bleeding time
thrombocytopenia
VWD
platelet dysfunction
vascular dysfunction
Prothrombin time
- platelet poor plasma obtained from blood sample
- citrate
- tissue factor, phospholipid, calcium as reagents
- time to clot detection
- sensitive to factor VII
How does warfarin affect PT?
elevated PT
- affects factor VII
What does heparin do?
binds AT III which binds anti-coag factors in intrinsic and extrinsic
How does heparin affect PT?
elevated PT
What are the common pathway factors?
I (fibrinogen), II, V, X
1x2x5=10
What happens if you don’t have enough fibrinogen
prolonged PT
- fibrin isn’t adequately getting properly formed
What do inhibitors lead to?
elevated PT
How do you calculate INR
PT/PT(normal) raised to the ISI (international sensitivity index)
What is added to the tube when checking for aPTT
- add an activator - silica, kaolin
- phospholipid
- calcium
- tissue factor is not used
What can elevated FVIII cause to the aPTT
shortened
What does a FVIII inhibitor do to PTT
elevated aPTT
How is thrombin time measured?
thrombin and calcium are added to the plasma
- measure clot formation
- conversion of fibrinogen to fibrin
What can cause an elevated thrombin time
heparin
How would dysfibrinogenemia/hypofibrinogemia affect thrombin time
elevated thrombin time
How can you confirm that a prolonged TT is due to heparin?
test using reptilase will be normal
What will the TT and the reptilase be in dysfibrinogemia?
TT and reptilase are prolonged and immunologic assay for fibrinogen will be normal
What are autoantibodies specific to?
lupus-like type or secondary to an underlying autoimmune disorder
What are alloantibodies
anti-factor VIII in a patient with hemophilia A following factor VIII concentrate infusion
what is the autoantibody specificity of lupus-like coagulant?
plasma beta2-glycoprotein I which binds to coagulation factors
What is PF4?
neutralizes heparin in heparin level determination
- when samples aren’t properly spun down
How quickly should assays be run?
less than 2 hours because factor V and VIII are labile
what is the steps of the mixing study
first exclude heparin
- immediate and incubate mixture of patient and normal plasma
- see if it corrects
What would lupus anticoagulant cause in the mixing study
won’t correct
- nonspecific inhibitor
Patient with PT of 22 sec, PTT of 67
- normal fibrinogen
- no recent history of coumadin or heparin
- mixing study: PT: 13 sec, PTT: 32 sec
factory deficiency because correction of PT and PTT
How do you test for lupus-like anticoagulant
factory specific inhibitor
Which 3 factors are not associated with bleeding?
factor XII, prekallikrein, kininogen are not associated with bleeding
What does the factor V leiden mutation cause?
resistance to protein C
- increase inability to clot
protein S/C deficiency
less ability to activate factor V = more clotting
ATIII
major inhibitory protein for clotting cascade
lupus anticoagulant
LA = immunoglobulin which interfere with steps of clotting resulting in prolonged coagulation
What causes the antiphospholipid antibody syndrome?
increase in cardiolipin and beta2-glycoprotein I antibodies
What does APS criteria require
1 clinical and 1 laboratory finding
