Hemostasis Testing

Question 1

How does the presence of FDPs inhibit clotting in coagulation testing?

Answer 1

Interfere with
fibrin polymerization

Question 2

A patient is given an excess of urokinase. What would you expect of the PT and APTT
results and why?

Answer 2

both increased because plasmin breaks down fibrinogen

Question 3

What test will determine total fibrinogen levels (including dysfunctional)?

Answer 3

immunological fibrinogen

Question 4

How do you differentiate HIT from HITTS?

Answer 4

HIT - PLT 100,000 1-3 days after heparin

HITTS - PLT low 20,000 1-3 days after heparin (thrombosis)

Question 5

What does INR stand for and what is its purpose?

Answer 5

internationalized ratio: std patient PT results between labs

Question 6

How does the Reptilase Time differ from the Thrombin Time?

Answer 6

RT cleaves fibrinopeptides A/B and is not inhibited by thrombin inhibitors such as heparin

Question 7

Which of the platelet agonists should result in a longer lag phase and a single phase
aggregometry graph in 100% of normal subjects after the agent is added to PRP

Answer 7

Collagen

Question 8

Which test is mostly used to monitor the effects of heparin

Answer 8

APTT or anti Xa activity

Question 9

What are PIVKAS and which screening test is most sensitive to their presence?

Answer 9

produced when pt is on an anticoag, PT is most sensitive to screen, ISI value based on sensitivity to pIVKAS

Question 10

If a factor XIII deficiency is suspected, what test should be performed and what is the
expected result in a deficiency

Answer 10

urea clot lysis - clot will lyse <24hr

Question 11

A patient has a normal APTT and a prolonged PT. A 50:50 mix was done and the PT was
repeated. The PT result was now within the normal reference range. What is the most
likely cause of the original abnormal result

Answer 11

VII deficiency

Question 12

TT tests for adequacy of

Answer 12

fibrinogen

Question 13

whuch procedure will test the common pathway?

Answer 13

RVVT

Question 14

What test is used to evaluate the body’s fibrinolytic ability

Answer 14

euglobulin clot lysis

Question 15

Which phospholipid dependent routine screening test is affected most by the presence
of a lupus inhibitor?

Answer 15

APTT

Question 16

How does sodium citrate act as an anticoagulant in the blue top tube and what must be
done in many hemostasis tests to overcome this effect

Answer 16

binds calcium, more must be added to overcome anticoag to participate in the cascade

Question 17

Which assay can distinguish between fibrinolysis and fibrinogenolysis? And what are the
expected results

Answer 17

D dimer (pos in only fibrinolysis)

Question 18

What is the advantage of direct factor Xa inhibitors over other antithrombotic
therapies?

Answer 18

doesnt need to be monitored by tests except special circumstances

Question 19

What are the possible deficient factors is both the PT and APTT are prolonged

Answer 19

I, II, V, X

Question 20

What does freeze/thawing of donor platelets do in the platelet neutralization
procedure?

Answer 20

Corrected time, used to confirm DVVT/KCT, allows binding

Question 21

In what situation would a 50:50 mix be performed and how would you interpret the
results?

Answer 21

If one of the coagulation screening tests (PT, APTT, TT) is prolonged. If the time
to clot corrects toward normal - it is a factor deficiency, if there is no significant
correction - it is an inhibitor.

Question 22

What is the major difference in reporting for the fibrinogen assay vs. the thrombin time

Answer 22

Both assays test the conversion of fibrinogen to fibrin by adding thrombin as a reagent.
The time for the clot to form is recorded in seconds, but in the fibrinogen assay the time
to clot is converted to mg/dL of fibrinogen

Question 22

Which factor is NOT tested for in routine coagulation screening tests

Answer 22

XIII

Question 23

In platelet aggregation study, platelet agonist is added. For patient on anti-inflammatory
drugs therapy (such as aspirin), what type of pattern is commonly seen

Answer 23

no secondary phase due to inadequate aggregation

Question 24

List the normal stages of platelet aggregation seen in on a platelet aggregometer

Answer 24

primary wave of aggregation, release reaction (shoulder) and secondary wave of aggregation

Question 25

What is the primary difference in clot detection using photo-optical vs. mechanical (such as magnetically monitoring) instrumentation

Answer 25

? Photo-optical detects the clot through a change in optical density when the clot forms (the specimen becomes cloudy) vs. mechanical methods detect clot formation by the physical stoppage of a steel ball’s movement (or completion of an electric circuit when a clot is formed)

Question 26

What test (other than a mixing study) can be used to differentiate a lack of fibrinogen from the presence of an inhibitor such as heparin

Answer 26

RT

Question 27

What test(s) would need to be done to detect a fibrinogen dysfunction

Answer 27

TT would be prolonged or Fibrinogen activity would be low. Immunological fibrinogen (measures total – not just functional) would be normal or increase

Question 28

In platelet aggregation studies, how does ristocetin act differently than the other aggregating agents used?

Answer 28

All other aggregating agents actually initiate platelet aggregation, whereas ristocetin is actually measuring platelet agglutination (platelet sticking to platelet via GP1b and vWF)

Question 29

A patient has a known Factor IX deficiency, but when an MLS conducts a PFA-100, the result falls within the normal reference range. Should it be assumed that the MLS performed the test incorrectly, should it therefore be repeated and why

Answer 29

The MLS did not perform the test incorrectly and it should not be repeated. The PFA was normal because a Factor IX deficiency does not affect the platelets and platelet function is what is being tested in the PFA

Question 30

Why is a 50:50 for an APTT read initially and then incubated at 37 degrees for 30 min to 1 hour before they are repeated

Answer 30

VIII/LI are time and temp dependent, may not show inhibition unless incubated

Question 31

What type of deficiencies would you expect from a patient with no bleeding problems and an increased APTT? Explain this phenomenon.

Answer 31

XII, PK, HMWK, thrombosis due to inactivation of plasminogen

Question 32

What is pNA and in which assay (that we discussed in class) is it used

Answer 32

d? pNA stands for Para-nitroalinine, and it is used as a color-producing agent in the Chromogenic Hemostasis Assay. It is used in the Anti-Xa assay. It produces color when cleaved by factor X

Question 33

Why is it that a prothrombin time, which tests the extrinsic pathway, is unable to test for Tissue Factor III, Calcium or Platelet factor

Answer 33

because they are added as part of the reagent (thromboplastin/neoplastine/innovin)

Question 34

What is the role of each reagent in the activated partial thromboplastin time

Answer 34

Activator reagent – substance such as ellagic acid or kaolin mimics the activation of XII by collagen. It also contains phospholipid that acts as a Platelet Factor 3 substitute. o CaCl2 – completes the tenase and prothrombinase complexes (needed in the intrinsic part of the cascade.)

Question 35

A 50-year-old man has been on heparin for the past 7 days. Which of the following test(s) would you expect to be abnormal? PT, APTT, Thrombin time, or fibrinogen assay

Answer 35

PT, APTT, TT prolonged fibrinogen assay will not be affected as it is diluted 1:10 to minimize inhibitors

Question 36

When performing a Factor VIII activity assay, patient plasma is mixed with what substance?

Answer 36

VIII deficient plasma