Deck 45: Laboratory Evaluation of Hemostasis

Question 1

A prolonged PTT is corrected when mixed with normal plasma and tested immediately and after a 2-hour incubation. Which test (or tests) should be performed next?

A) Bethesda titer
B) High phospholipid PTT
C) Anti-Xa assay
D) Factor VIII and IX assays

Answer 1

Factor VIII and IX assays

Question 2

A patient's platelet count drops 4 days after being placed on heparin. Select the correct interpretation.

A) The patient has heparin-induced thrombocytopenia.
B) The patient has benign, limited thrombocytopenia related to heparin.
C) A bleeding time should be performed to evaluate qualitative platelet disorders.
D) An immunoassay for heparin-dependent anti-platelet factor 4 (PF4) should be performed to distinguish heparin-induced thrombocytopenia from benign, limited thrombocytopenia related to heparin.

Answer 2

An immunoassay for heparin-dependent anti-platelet factor 4 (PF4) should be performed to distinguish heparin-induced thrombocytopenia from benign, limited thrombocytopenia related to heparin.

Question 3

Which of the following is an acceptable sample for testing on a photo-optical clot-detecting instrument?

A) Lipemic plasma
B) Hemolyzed plasma
C) Serum
D) Plasma collected using a 9:1 ratio of whole blood to 3.2% sodium citrate

Answer 3

Plasma collected using a 9:1 ratio of whole blood to 3.2% sodium citrate

Question 4

Which of the following would likely have a normal PT?

A) Patient with a factor VII deficiency
B) Patient with a factor VIII deficiency
C) Patient on warfarin
D) Clotted blood

Question 5

A patient sample has normal platelet aggregation patterns for all agonists except that no reaction occurs with ristocetin. Ristocetin agglutination is not corrected with exogenous VWF. What condition is most likely?

A) VWD
B) Storage pool disorder
C) Bernard-Soulier syndrome
D) Aspirin use

Question 6

Patients with which of the following would have a normal PT?

A) Liver disease
B) Disseminated intravascular coagulation (DIC)
C) Factor VII deficiency
D) Factor IX deficiency

Question 7

The bleeding time result will be normal and thus of no value to perform in patients who have:

A) A qualitative platelet disorder
B) von Willebrand disease (VWD)
C) Glanzmann thrombasthenia
D) Factor VIII deficiency

Question 8

Which of the following will cause spuriously prolonged clot-based coagulation tests?

A) An evacuated 3.2% sodium citrate tube filled to 50% capacity
B) An evacuated 3.2% sodium citrate tube filled to 90% capacity
C) Prolonged tourniquet application
D) Plasma collected from a traumatic tap

Question 9

How often must the partial thromboplastin time (PTT) reference interval be determined?

A) Only when both the normal and abnormal controls are outside their acceptable limits
B) At least every 6 months
C) With each new lot of reagent
D) Only when the normal control is outside its acceptable limits

Question 10

A platelet aggregation study shows diminished response to all agonists except for a small response to arachidonic acid and full response to ristocetin. Which condition is most likely?

A) Glanzmann thrombasthenia
B) Aspirin use
C) VWD
D) Platelet release defect

Question 11

Which of the following is an acceptable sample for a prothrombin time (PT) test?

A) One that was collected 22 hours before testing and stored at room temperature
B) One with a very small clot that was easily removed
C) 3.2% Sodium citrate blood sample immediately collected following a serum separator tube
D) Blood anticoagulated with heparin and brought to the laboratory within 1 hour

Question 12

A patient admitted to the hospital with thrombosis is given the standard heparin dosage. Twenty-four hours after the heparin is started, the PTT is 38 seconds (reference range, 25 to 37 seconds). Both normal and abnormal controls are within their limits. Which of the following is most likely?

A) Laboratory error
B) Patient has low antithrombin
C) Heparin-induced thrombocytopenia
D) Patient should be switched to low-molecular-weight heparin (LMWH)

Question 13

A patient is stabilized on warfarin with an international normalized ratio (INR) of 2.7. He develops pneumonia and is admitted to the hospital. His appetite is depressed and he is placed on broad-spectrum antibiotic agents. At 1 week after the admission, his INR is 5.0. What is the most likely interpretation?

A) The patient should be given more warfarin.
B) A PTT should be performed to rule out heparin administration.
C) A new sample should be collected to rule out a clotted specimen.
D) Vitamin K is reduced, increasing the effects of warfarin.

Question 14

Which of the following is necessary for normal platelet aggregation?

A) Ristocetin
B) von Willebrand factor (VWF)
C) Epinephrine
D) Fibrinogen

Question 15

How often must controls be run for the PT and PTT?

A) With each patient sample
B) At least once per 8-hour shift
C) At least once per 24 hours
D) With each batch of 10

Question 16

What is the test commonly used to monitor the high heparin doses used in cardiac bypass surgery?

A) PTT
B) Prothrombin time
C) Thrombin clotting time
D) Fibrinogen

Question 17

Which of the following is good practice in regard to phlebotomy on patients with hemostasis testing ordered?

A) Make sure the patient is fasting.
B) Always draw the sodium citrate tube last.
C) Collect the blood in a glass syringe.
D) Use a 20- or 21-gauge needle.

Question 18

Which of the following is acceptable practice regarding collection of blood when using a syringe and winged needle set?

A) Blood can be transferred to evacuated tubes once the phlebotomist returns to the laboratory.
B) Evacuated tubes must be placed in a rack when filling.
C) The first 20 mL collected must be discarded.
D) The evacuated tube stopper is removed, and blood is squirted into the tube using a 24-gauge needle.

Question 19

Which of the following conditions would have a normal PTT?

A) Lupus anticoagulant
B) Fibrinogen of 50 mg/dL
C) Factor VII deficiency
D) Heparin therapy

Question 20

A patient has a hematocrit of 65%. Which of the following is true related to coagulation testing?

A) Hematocrit does not affect coagulation testing.
B) Tube must be recollected with heparin as the anticoagulant.
C) Tube must be recollected using 0.34 mL of sodium citrate to 4.5 mL of blood.
D) Tube must be recollected using 0.62 mL of sodium citrate to 4.5 mL of blood.

Question 21

Which of the following deficiencies prolongs the PTT but does not lead to abnormal bleeding?

A) Factor V
B) Factor VIII
C) Factor XI
D) Factor XII

Question 22

Standard curves are necessary for which coagulation procedures?

A) Thrombin time
B) Specific factor assays
C) Fibrinogen assay
D) Both specific factor assays and fibrinogen assay

Question 23

A patient is positive for fibrin degradation products and negative for D dimers. Which condition is most likely?

A) Systemic fibrinolysis
B) DIC
C) Hypofibrinogenemia
D) Deep vein thrombosis (DVT)

Question 24

A patient has an elevated thrombin time and normal reptilase time. Which of the following situations is most likely?

A) Heparin therapy
B) Low fibrinogen
C) Elevated fibrin split products
D) Dysfibrinogenemia

Question 25

Which of the following conditions is associated with an elevated fibrinogen?

A) Acute DIC
B) Chronic inflammation
C) Severe liver disease
D) Increased plasmin levels

Question 26

Which of the following specimens would be acceptable for platelet aggregation studies?

A) Blood drawn in ethylenediaminetetraacetic acid (EDTA) and kept at room temperature for 6 hours
B) Blood drawn in 3.2% sodium citrate and transported to the laboratory on ice (2 $\degree$ to 4 $\degree$ C)
C) Blood drawn in a serum separator tube
D) Blood drawn in 3.2% sodium citrate and kept at room temperature for 2 hours after drawing

Question 27

The urea solubility test evaluates factor:

A) I
B) V
C) X
D) XIII

Question 28

An elevated tissue plasminogen activator (TPA) is associated with:

A) Abnormal bleeding
B) Aspirin use
C) DIC
D) Decreased fibrinolysis

Question 29

A 53-year-old woman arrives at the hospital with bleeding into the back of the throat and has a coagulation screen performed. She has no history of abnormal bleeding before this despite major stress to hemostasis in the past: she was in a major automobile accident at age 37 and has had impacted wisdom teeth extracted. Her coagulation results follow:

Which of the following is the most likely cause for her bleeding?

A) Factor XII deficiency
B) Factor IX deficiency
C) Factor VIII deficiency
D) Factor VIII inhibitor

Question 30

A patient has a factor VIII level of 50% activity. Which is most likely true regarding what can be expected for this patient's clinical situation?

A) Severe bleeding
B) Moderate bleeding
C) Mild bleeding
D) Normal with respect to factor VIII