Hemostasis Testing Flashcards
How does the presence of FDPs inhibit clotting in coagulation testing?
Interfere with
fibrin polymerization
A patient is given an excess of urokinase. What would you expect of the PT and APTT
results and why?
both increased because plasmin breaks down fibrinogen
What test will determine total fibrinogen levels (including dysfunctional)?
immunological fibrinogen
How do you differentiate HIT from HITTS?
HIT - PLT 100,000 1-3 days after heparin
HITTS - PLT low 20,000 1-3 days after heparin (thrombosis)
What does INR stand for and what is its purpose?
internationalized ratio: std patient PT results between labs
How does the Reptilase Time differ from the Thrombin Time?
RT cleaves fibrinopeptides A/B and is not inhibited by thrombin inhibitors such as heparin
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
Collagen
Which test is mostly used to monitor the effects of heparin
APTT or anti Xa activity
What are PIVKAS and which screening test is most sensitive to their presence?
produced when pt is on an anticoag, PT is most sensitive to screen, ISI value based on sensitivity to pIVKAS
If a factor XIII deficiency is suspected, what test should be performed and what is the
expected result in a deficiency
urea clot lysis - clot will lyse <24hr
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
VII deficiency
TT tests for adequacy of
fibrinogen
whuch procedure will test the common pathway?
RVVT
What test is used to evaluate the body’s fibrinolytic ability
euglobulin clot lysis
Which phospholipid dependent routine screening test is affected most by the presence
of a lupus inhibitor?
APTT
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
binds calcium, more must be added to overcome anticoag to participate in the cascade
Which assay can distinguish between fibrinolysis and fibrinogenolysis? And what are the
expected results
D dimer (pos in only fibrinolysis)
What is the advantage of direct factor Xa inhibitors over other antithrombotic
therapies?
doesnt need to be monitored by tests except special circumstances
What are the possible deficient factors is both the PT and APTT are prolonged
I, II, V, X
What does freeze/thawing of donor platelets do in the platelet neutralization
procedure?
Corrected time, used to confirm DVVT/KCT, allows binding
In what situation would a 50:50 mix be performed and how would you interpret the
results?
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.
What is the major difference in reporting for the fibrinogen assay vs. the thrombin time
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
Which factor is NOT tested for in routine coagulation screening tests
XIII
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
no secondary phase due to inadequate aggregation
List the normal stages of platelet aggregation seen in on a platelet aggregometer
primary wave of aggregation, release reaction (shoulder) and secondary wave of
aggregation
What is the primary difference in clot detection using photo-optical vs. mechanical (such
as magnetically monitoring) instrumentation
? 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)
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
RT
What test(s) would need to be done to detect a fibrinogen dysfunction
TT would be
prolonged or Fibrinogen activity would be low. Immunological fibrinogen (measures
total – not just functional) would be normal or increase
In platelet aggregation studies, how does ristocetin act differently than the other
aggregating agents used?
All other aggregating agents actually initiate platelet
aggregation, whereas ristocetin is actually measuring platelet agglutination (platelet
sticking to platelet via GP1b and vWF)
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
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
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
VIII/LI are time and temp dependent, may not show inhibition unless incubated
What type of deficiencies would you expect from a patient with no bleeding problems
and an increased APTT? Explain this phenomenon.
XII, PK, HMWK, thrombosis due to inactivation of plasminogen
What is pNA and in which assay (that we discussed in class) is it used
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
Why is it that a prothrombin time, which tests the extrinsic pathway, is unable to test
for Tissue Factor III, Calcium or Platelet factor
because they are added as part of the reagent (thromboplastin/neoplastine/innovin)
What is the role of each reagent in the activated partial thromboplastin time
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.)
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
PT, APTT, TT prolonged
fibrinogen assay will not be affected as it is diluted 1:10 to minimize inhibitors
When performing a Factor VIII activity assay, patient plasma is mixed with what
substance?
VIII deficient plasma
