Tests

Question 1

Deficiencies that cause prolonged PTT with normal PT

Answer 1

VWF, hemophilia A, hemophilia B, Factor 11

Question 2

Causes of prolonged PTT that do not cause bleeding

Answer 2

Lupus anticoagulant’s, and contact factors (factor 12, prekallikrein, high molecular weight Kallikrein)

Question 3

Test for factor 13 deficiency

Answer 3

5M urea solubility test

Question 4

PT

Answer 4

Measures factors in an extrinsic pathway, prolongation can be caused by deficiencies in factors seven, 10, five, two and, one

Question 5

PTT reagents

Answer 5

Plasma activator (kaolin, diatomaceous earth to provide negative charge) and phospholipid, calcium chloride is added last

Question 6

PT panic value

Answer 6

INR greater than 5

Question 7

PTT panic value

Answer 7

Greater than 60s

Question 8

Fibrinogen measurement method

Answer 8

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

Question 9

Fibrinogen panic value

Answer 9

Less than 100 mg/dL

Question 10

Modified citrate tube

Answer 10

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

Question 11

Heparin neutralization can be used for what tests?

Answer 11

PT, PTT, and fibrinogen

Question 12

Causes of prolonged thrombin time

Answer 12

Therapeutic heparin regimens, increased fibrin degradation products, hypofibrinogenemia

Question 13

Reptilase test uses

Answer 13

This test is not inhibited by heparin and so can differentiate between patients on heparin therapy and those with hypo or dysfibrinogenemia

Question 14

Lupus anticoagulant testing

Answer 14

Brussels viper venom test and hexa

Question 15

Lupus anticoagulant affects

Answer 15

Phospholipid dependent inhibitor, causes prolonged PTT

Question 16

Tests for DIC

Answer 16

D dimer, fibrinogen, TT, platelet levels

Question 17

Tests for DVT

Answer 17

D dimer, with a cut off of less than 400

Question 18

RVVT

Answer 18

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

Question 19

Platelet aggregation agonists

Answer 19

ADP, ristocetin, epinephrine, collagen and thrombin

Question 20

Aspirin interference

Answer 20

Interferes with cyclooxygenase enzymes so that arachidonic acid cannot be converted to thromboxane A2, which stimulates platelet aggregation

Question 21

Activated clotting time

Answer 21

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

Question 22

Thrombophilia screening tests

Answer 22

Antithrombin III, protein C, protein S

Should be drawn after anticoagulant therapy has been administered

Question 23

INR calculation

Answer 23

[(patient PT)/(control PT)]^ISI

Question 24

Recombinant tPA use

Answer 24

Used in cases of clotting to prevent stroke or pulmonary embolism, converts plasminogen to plasmin to stimulate clot break down

Question 25

Insensitive screening test for fibrinolysis

Answer 25

Euglobulin clot lysis

Question 26

Why would you run a low fibrinogen test?

Answer 26

The fibrinogen level is under 60, due to problems with linearity

Question 27

Causes of PTT results greater than 100

Answer 27

Clotted samples, QNS, drawing through a line (heparin contamination)

Question 28

How do you monitor warfarin and heparin therapy in patients with lupus anticoagulant’s?

Answer 28

Warfarin is monitored by chromogenic factor X, heparin is monitored by anti-factor XA, known as heparin assays

Question 29

What is the principle of the platelet aggregation test?

Answer 29

Platelets will release ADP from their granules, which stimulates the platelets to aggregate