Hemostasis Testing Flashcards

1
Q

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

A

Interfere with
fibrin polymerization

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2
Q

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

A

both increased because plasmin breaks down fibrinogen

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3
Q

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

A

immunological fibrinogen

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4
Q

How do you differentiate HIT from HITTS?

A

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

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

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5
Q

What does INR stand for and what is its purpose?

A

internationalized ratio: std patient PT results between labs

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6
Q

How does the Reptilase Time differ from the Thrombin Time?

A

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

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7
Q

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

A

Collagen

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8
Q

Which test is mostly used to monitor the effects of heparin

A

APTT or anti Xa activity

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9
Q

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

A

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

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10
Q

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

A

urea clot lysis - clot will lyse <24hr

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11
Q

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

A

VII deficiency

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12
Q

TT tests for adequacy of

A

fibrinogen

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13
Q

whuch procedure will test the common pathway?

A

RVVT

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14
Q

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

A

euglobulin clot lysis

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15
Q

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

A

APTT

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16
Q

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

A

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

17
Q

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

A

D dimer (pos in only fibrinolysis)

18
Q

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

A

doesnt need to be monitored by tests except special circumstances

19
Q

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

A

I, II, V, X

20
Q

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

A

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

21
Q

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

A

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.

22
Q

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

A

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

22
Q

Which factor is NOT tested for in routine coagulation screening tests

A

XIII

23
Q

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

A

no secondary phase due to inadequate aggregation

24
Q

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

A

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

25
Q

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

A

? 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)

26
Q

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

A

RT

27
Q

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

A

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

28
Q

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

A

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

29
Q

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

A

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

30
Q

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

A

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

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

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

34
Q

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

A

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.)

35
Q

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

A

PT, APTT, TT prolonged

fibrinogen assay will not be affected as it is diluted 1:10 to minimize inhibitors

36
Q

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

A

VIII deficient plasma