Tests Flashcards
(29 cards)
Deficiencies that cause prolonged PTT with normal PT
VWF, hemophilia A, hemophilia B, Factor 11
Causes of prolonged PTT that do not cause bleeding
Lupus anticoagulant’s, and contact factors (factor 12, prekallikrein, high molecular weight Kallikrein)
Test for factor 13 deficiency
5M urea solubility test
PT
Measures factors in an extrinsic pathway, prolongation can be caused by deficiencies in factors seven, 10, five, two and, one
PTT reagents
Plasma activator (kaolin, diatomaceous earth to provide negative charge) and phospholipid, calcium chloride is added last
PT panic value
INR greater than 5
PTT panic value
Greater than 60s
Fibrinogen measurement method
Clauss clotting method, in the presence of excess thrombin the clotting time deluded plasma is inversely proportional to the level of plasma fibrinogen. The clot is detected by electromagnetic viscosity and the Time is compared to a standard curve
Fibrinogen panic value
Less than 100 mg/dL
Modified citrate tube
If the hematocrit is too high there is too much citrate for the amount of plasma, after deciding how much blood is needed for the tests, you can calculate how much citrate is needed:
X = [(100-Hct)/(595-Hct)] x 100
Remove citrate from the tube so the “X” value is left, then calculate how much blood to draw based on citrate present
Heparin neutralization can be used for what tests?
PT, PTT, and fibrinogen
Causes of prolonged thrombin time
Therapeutic heparin regimens, increased fibrin degradation products, hypofibrinogenemia
Reptilase test uses
This test is not inhibited by heparin and so can differentiate between patients on heparin therapy and those with hypo or dysfibrinogenemia
Lupus anticoagulant testing
Brussels viper venom test and hexa
Lupus anticoagulant affects
Phospholipid dependent inhibitor, causes prolonged PTT
Tests for DIC
D dimer, fibrinogen, TT, platelet levels
Tests for DVT
D dimer, with a cut off of less than 400
RVVT
Snake venom activates F10, with phospholipid and F5. This converts prothrombin to thrombin. Thrombin converts fibrinogen to fibrin. If lupus anticoagulant are present they will bind the phospholipid in the test and the clotting time will be prolonged
Platelet aggregation agonists
ADP, ristocetin, epinephrine, collagen and thrombin
Aspirin interference
Interferes with cyclooxygenase enzymes so that arachidonic acid cannot be converted to thromboxane A2, which stimulates platelet aggregation
Activated clotting time
Used for heparin monitoring, diatomaceous earth is placed in the Vacutainer before patient is drawn, once whole blood is out of the tube is tilted and timed until clotting occurs
Thrombophilia screening tests
Antithrombin III, protein C, protein S
Should be drawn after anticoagulant therapy has been administered
INR calculation
[(patient PT)/(control PT)]^ISI
Recombinant tPA use
Used in cases of clotting to prevent stroke or pulmonary embolism, converts plasminogen to plasmin to stimulate clot break down
