Question 1

It has been determined that a patient has activated protein C resistance. Name the most prevalent genetic mutation associated with this finding.

Accepted Answer

Activated protein C resistance is most commonly caused by a genetic mutation in the factor V protein, specifically a substitution of arginine to glutamine at the 506 position, also known as factor V Leiden.

Question 2

Failure of protein C to destroy FVa and FVIIIa results in an increase in what hemostatic system alteration?

Accepted Answer

Protein C normally acts to destroy coagulation factors FVa and FVIIIa, which are necessary for the production of thrombin. When protein C is unable to carry out this function, there is an increase in thrombin production, leading to a procoagulant state. Platelets, FVIII, and FXa may be involved in this process, but the primary alteration is the increase in thrombin.

Question 3

When is routine monitoring of LMWH indicated?

Accepted Answer

Routine monitoring of Low Molecular Weight Heparin (LMWH) is indicated in special populations such as those with obesity, pediatric patients, and individuals with renal insufficiency. These conditions can alter the pharmacokinetics of LMWH, necessitating closer monitoring to ensure efficacy and minimize the risk of adverse effects.

Question 4

A patient has been diagnosed with a coagulopathy and has been given Coumadin as a mode of treatment. What screening test(s) should be performed to monitor this treatment, and what effect will this therapy have on the coagulation pathway?

Accepted Answer

The answer of A patient has been diagnosed with a...

Question 5

Antithrombin and heparin cofactor II primarily inhibit which of the following factors?

Accepted Answer

Antithrombin and heparin cofactor II primarily inhibit factors IXa, Xa, and thrombin, thus reducing the formation of fibrin.

Question 6

Which of the following test results would help differentiate between type I and II protein C deficiencies?

Accepted Answer

The answer of Which of the following test results would...

Question 7

A tendency to favor thrombus formation produced from an imbalance in the major constituents of the hemostatic system is defined as:

Accepted Answer

Thrombophilia is the condition where there is a predisposition to forming blood clots due to an imbalance in the hemostatic system.

Question 8

During coumadin-induced anticoagulation, which factor's activity disappears most rapidly?

Accepted Answer

FVII has the shortest half-life among vitamin K-dependent coagulation factors and its activity usually disappears within 2-4 hours of taking warfarin.

Question 9

Which of the following is thought to be a traditional risk factor associated with the formation of arterial thrombi?

Accepted Answer

Diabetes is a traditional risk factor associated with the formation of arterial thrombi. It may cause damage to the arterial walls and increase inflammation, leading to an increased risk of thrombosis. Von Willebrand's disease, Hemophilia, and Dysfibrinogenemia are all inherited bleeding disorders and are not typically associated with an increased risk of arterial thrombosis.

Question 10

How do red thrombi differ from white thrombi?

Accepted Answer

Red thrombi primarily consist of red blood cells and are typically found in venous systems, while white thrombi are rich in platelets and fibrin, often forming in arterial or high-flow areas, indicating differences in both location and composition.

Question 11

A patient has been taking Coumadin for a recent thrombophilic episode. He follows up with his physician two weeks after starting this treatment. The physician sees evidence of skin necrosis on the patient. What should the physician do next to investigate this finding?

Accepted Answer

Skin necrosis is a rare but serious side effect of Coumadin use, known as Coumadin-induced skin necrosis (CISN). It occurs due to rapid depletion of protein C and protein S, which are vitamin K-dependent anticoagulants. Therefore, the physician should investigate the patient's protein C levels by requesting a Protein C antigen assay. This test measures the amount of protein C circulating in the blood and can help identify a deficiency that may contribute to CISN. PT and APTT measure the clotting time of blood and do not specifically test for protein C or protein S levels. HC-II antigen assay tests for the presence of heparin cofactor II, which can inhibit thrombin activity and is not directly related to CISN.

Question 12

Which of the following alterations would most likely be associated with a hypercoagulable state?

Accepted Answer

Hypercoagulable states are associated with an excess of plasma coagulation proteins, which can lead to an increase in clot formation. Options B, C, and D are associated with an increased risk of bleeding and do not contribute to a hypercoagulable state.

Question 13

A patient with thrombophilia has a decreased functional and antigenic activity of protein C. What is the diagnosis?

Accepted Answer

Thrombophilia with decreased functional and antigenic activity of protein C indicates Type I PC deficiency, which is a quantitative deficiency of protein C. It is different from Type II PC deficiency, which is a qualitative deficiency of protein C. APCR and Protein S deficiency are also possible causes of thrombophilia, but the given information specifically indicates a deficiency in protein C.

Question 14

Patients with a DVT are at risk for developing which of the following?

Accepted Answer

Patients with DVT are at risk for developing pulmonary emboli, which occur when the blood clot travels to the lung and blocks blood flow. The other choices are not typically associated with DVT.

Question 15

Mutations in which of the following gene(s) lead to hyperhomocysteinemia?

Accepted Answer

Mutations in CBS and MTHFR genes lead to hyperhomocysteinemia. HFE gene mutations are associated with hereditary hemochromatosis, while prothrombin and factor V gene mutations are associated with clotting disorders.

Question 16

Heparin inhibits coagulation by:

Accepted Answer

Heparin catalyzes the activity of antithrombin III, which in turn inhibits the activity of thrombin and other coagulation factors, ultimately leading to the prevention of blood clot formation.

Question 17

What is the usual adjustment for heparin dosage?

Accepted Answer

The usual adjustment for heparin dosage is aimed at achieving a PTT (partial thromboplastin time) that is 1.5-2.5 times the patient's pretreatment baseline PTT value. This range ensures effective anticoagulation while minimizing the risk of bleeding.

Question 18

A 30-year-old patient is diagnosed with a third episode of DVT. He is currently hospitalized and receiving heparin therapy. The physician orders a thrombotic risk battery of tests. What is the most appropriate action that the laboratory professional should take?

Accepted Answer

Testing for inherited thrombophilia during an acute thrombotic episode or while on anticoagulant therapy can lead to inaccurate results. Certain tests, such as those for protein C, protein S, and antithrombin deficiency, can be affected by these conditions, leading to false normal or abnormal results. Therefore, it is most appropriate to communicate with the physician about the limitations of testing under these circumstances.

Question 19

Patients with protein C and/or S deficiencies are at risk for which type of complication?

Accepted Answer

Protein C and S deficiencies increase the risk of thrombosis (blood clots), not hemorrhage, delayed bleeding after injury, or fibrinolysis.

Question 20

A postoperative heart transplant patient has been given unfractionated heparin. Five days postoperative, he develops petechiae and needs multiple dressing changes over his wound site. What tests should be used to assess the patient's clinical status?

Accepted Answer

The patient's symptoms suggest he may have heparin-induced thrombocytopenia (HIT), which is associated with unfractionated heparin use. The appropriate tests to assess for HIT are a platelet count and HIT antibody assay. APTT and PT measure coagulation factors, while PT and FDP measure fibrinolysis; these tests are not specific for HIT. D-dimer and fibrinogen levels are also not specific for HIT.

Quiz 35: Thrombophilia