MLS 4230 Coag Exam 1 Media Labs and Primary Hemostasis Disorders

What is the normal platelet count?

150k-400k

A patient who is on low-dose aspirin therapy normally exhibits which of these changes in blood platelets? A. Altered platelet function B. Decrease in platelet concentration C. Platelet clumps observed on a peripheral blood smear D. Platelet satellitism observed on a peripheral blood smear

A. Altered platelet function

Which of the following may be a cause of aspirin non-responsiveness? A. Buildup of plaque in blood vessels B. Use of uncoated aspirin tablets C. Taking more than the prescribed dosage of aspirin D. A low platelet count

A. Buildup of plaque in blood vessels

What is the function of the ADAMTS13 enzyme? A. Cleaving ultra-large molecules of von Willebrand factor to keep them out of circulation B. Breaking down fibrinogen C. Transporting antibody-coated platelets to the spleen D. Contributing to the maturation of megakaryocytes

A. Cleaving ultra-large molecules of von Willebrand factor to keep them out of circulation

What enzyme is inhibited when the production of thromboxane A2 is blocked by ingested aspirin? A. Cyclooxygenase-1 B. Acetaldehyde dehydrogenase C. CYP2D6 D. CYP2C9

A. Cyclooxygenase-1

Which of the following processes can lead to the formation of microclots in a patient specimen that is collected in a tube containing EDTA anticoagulant? A. Failing to invert the tube after specimen collection B. Filling the tube as full as the vacuum in the tube allows C. Inverting the tube 5-10 times after specimen collection D. Using the EDTA tube for an automated platelet count

A. Failing to invert the tube after specimen collection Feedback Failing to invert a tube containing an anticoagulant such as EDTA can cause the formation of microclots. This can result in a falsely decreased platelet count. The other choices that are listed are all acceptable practices and will not cause the formation of microclots in an EDTA tube.

At what temperature should blood specimens for platelet function testing be held? A. -20-0 C B. 4-8 C C. 18-24 C D. -80 C

C. 18-24 C

Which one of the following is the mechanism for the production of platelet satellitism? A. An IgG antibody is directed against clotting factor VIII B. An IgG antibody is directed against von Willebrand factor (vWF) C. An IgG antibody is directed against GP IIb/IIIA on the platelet membrane D. An IgG antibody is directed against fibrinogen

C. An IgG antibody is directed against GP IIb/IIIA on the platelet membrane Feedback Platelet satellitism is a rare situation in which an IgG antibody is directed against the glycoprotein IIb/IIIa complex on the platelet membrane. The antibody-coated platelets rosette around neutrophils, causing a falsely low platelet count to be recorded with automated instrumentation. Monocytes may also show some rosetting. No antibodies are formed against Factor VIII, vWF, or fibrinogen that result in platelet satellitism.

What is seen in Myelophthisic disorders?

Left shift nRBCs Teardrop cells

What are some Myelophthisic disorders?

Leukemia Lymphoma Multiple Myeloma Metastatic carcinoma Myelofibrosis

Which of the following causes schistocyte formation in disseminated intravascular coagulation (DIC)? A. Degranulation of promyelocytes B. Excessive fever in patients with DIC C. Microthrombi disposition in small vessels D. Excessive platelet size

Microthrombi disposition in small vessels Feedback Schistocytes are the result of erythrocytic membrane damage caused by sheering of red blood cells as they pass through a fibrin mesh of clot formation occurring in the blood vessels. This occurs in DIC, TTP and HUS. Therefore, schistocytes may be seen in all three of these conditions

What disorders are a result from deficient platelet production?

Myelophthisic disorders Aplasia Ineffective Erythropoiesis Congenital disorders

Are quantitative or qualitative platelet disorders more commonly encountered?

Quantitative

What happens once platelets drop to 20k or less?

Spontaneous hemorrhage may occur

What happens to thrombopoietin (TPO) when the platelet count is normal?

TPO is removed from the plasma by TPO receptors on megakaryocytes

What are platelets regulated by?

Thrombopoietin (TPO)

T/F: Bone marrow biopsy is often indicated in Myelophthisic cases.

True

What happens once platelets reach <10k?

a life-threatening hemorrhage may occur

What happens once platelets drop to 50k-100k?

symptoms of thrombocytopenia may begin to manifest, such as bruising, petechiae, and purpura

Where is thrombopoietin (TPO) produced?

In the liver (with a little help from the spleen)

"A substance that can stimulate platelet activation: is a definition for which of the following terms? A. Analyte B. Agonist C. Anticoagulant D. Antagonist

B. Agonist

With which of these conditions or procedures may there be an increased number of megakaryocytes in the bone marrow but a decreased number of circulating platelets? A. Folic acid deficiency B. Aplastic anemia C. Radiation therapy D. Massive blood transfusion

A. Folic Acid Deficiency Feedback Pancytopenia is often seen with megaloblastic anemias caused by folic acid or vitamin B12 deficiency. Thrombopoiesis (as well as erythropoiesis and granulopoiesis) is ineffective. The bone marrow will contain normal or even increased megakaryocytes, but the number of platelets entering the peripheral circulation is decreased. In aplastic anemia, megakaryocytes are decreased in number in the bone marrow, leading to a decreased number of circulating platelets.Radiation therapy causes bone marrow hypoplasia. Platelets, as well as all other cell lines, are depressed. The effect is transient; the marrow will regenerate once the therapy has ended.A massive blood transfusion may also cause transient thrombocytopenia, but megakaryocytes will not be increased in the bone marrow.

What is actually being measured in the optical light transmission aggregometry method used for platelet function analysis? A. Increased light transmittance over time B. Decreased light transmittance over time C. Quantitative number of platelet aggregates D. Aspirin-coated platelet aggregates

A. Increased light transmittance over time

A platelet function assay is performed on an analyzer that utilizes two cartridges: a collagen-epinephrine cartridge and a collagen-ADP cartridge. A citrated patient sample from a patient known to be on aspirin therapy is added to each cartridge, and the time that it takes for complete occlusion of the aperture to occur (closing time) is measured and recorded. These results are obtained: Collagen-epinephrine cartridge = 250 s (Reference interval = <164 s) Collagen-ADP cartridge = 100 s (Reference interval = <116 s) What do these results suggest? A. Successful aspirin therapy B. Aspirin non-responsiveness C. Increased platelet concentration D. A CYP2C19 mutation is present

A. Successful aspirin therapy

The result of a test that measures 11-dehydrothromboxane B2 (11-dTXB2) in urine is elevated. What may this result indicate? A. The patient may be at increased risk for an ischemic cardiovascular event B. The patient is most likely at low risk for an ischemic cardiovascular event C. The patient is responding appropriately to antiplatelet aspirin therapy D. An ischemic cardiovascular event is not possible

A. The patient may be at increased risk for an ischemic cardiovascular event

What is the mechanism of heparin-induced thrombocytopenia (HIT)? A.Antibodies directed against platelet factor 4 (PF-4) and heparin complex B. Administration of toxic doses of heparin that destroy platelets C. Abrupt cessation of heparin therapy D. Antibodies directed against dense granules

A.Antibodies directed against platelet factor 4 (PF-4) and heparin complex Feedback HIT is a complication that may occur in some patients receiving heparin therapy. When heparin is administered to these patients, it forms an immune complex with platelet factor 4 (PF-4) that is released from the alpha granules in platelets. The body's immune system recognizes this complex as a foreign substance and forms an antibody against it. The antibody binds to this complex, and the platelets are destroyed.

A woman in labor is bleeding, has a very high fever, and is in danger of losing the fetus. Laboratory results include a platelet count of 15 × 109/L (normal platelet count = 150-450 × 109/L), prolonged PT and aPTT, decreased fibrinogen, and increased D-dimer. Her automated blood count was flagged for blood smear review, and the cells indicated by the arrows were seen on her peripheral smear, along with a decrease in the number of platelets present. What condition is suggested by these results? A. Thrombotic thrombocytopenic purpura (TTP) B. Hemolytic uremic syndrome (HUS) C. Disseminated intravascular coagulation (DIC) D. Immune thrombocytopenic purpura (ITP)

C. Disseminated intravascular coagulation (DIC) Feedback As we can see from this patient's laboratory test results, her D-dimer is elevated, her PT and aPTT are prolonged, her fibrinogen and platelet count are dramatically decreased. This is a classic profile for DIC. Thrombocytopenia and the presence of schistocytes on the peripheral blood smear are also associated with TTP and HUS, but the abnormal D-dimer and coagulation tests point to DIC.

Which of the following is usually used as an anticoagulant when specimens are collected for platelet function testing? A. Lithium heparin B. EDTA C. Sodium citrate D. An anticoagulated specimen should not be used

C. Sodium citrate

Removal of which of these organs may be a last resort treatment for a patient whose platelet count is less than 30 × 109/L as a result of chronic idiopathic thrombocytopenic purpura (ITP)? A.Gall bladder B. Pancreas C. Spleen D. A kidney

C. Spleen Feedback In ITP, antibodies develop that coat the platelets. The spleen produces macrophages whose Fc receptors recognize and destroy these antibody-coated platelets. Removing the spleen would decrease platelet destruction, but it is a last resort since the immunologic function of the spleen would also be lost. Removing the gall bladder, pancreas, or a kidney would not improve thrombocytopenia caused by ITP.

Why might a physician order CYP2C19 enzyme genotyping for a patient prior to prescribing clopidogrel? A. To determine if the patient's platelets are functioning properly B. To determine if the patient may have an allergy to clopidogrel C. To determine if the patient possesses a CYP2C19 mutation that would affect their response to clopidogrel D. To determine if the patient has an aspirin resistance

C. To determine if the patient possesses a CYP2C19 mutation that would affect their response to clopidogrel

What happens to TPO in thrombocytopenia?

Clearance of TPO is low --> the concentration of TPO increases to help megakaryocyte/platelet production

Which laboratory result is the most critical in recognizing heparin-induced thrombocytopenia (HIT)? A. Activated partial thromboplastin time B. Prothrombin time C. D-dimer D. Platelet count

D. Platelet count Feedback Patients receiving heparin therapy should have periodic platelet counts performed to detect possible HIT.The aPTT, PT, and D-dimer do not help detect HIT.

What is a corrective action that can be used to obtain a valid platelet count from a patient specimen that exhibits platelet satellitism on the manual differential? A. Redraw the patient specimen in another EDTA collection tube and wait 20 minutes before sampling. B. Refrigerate the patient sample for 30 minutes prior to sampling. C. Invert the EDTA tube several times prior to sampling. D. Recollect the blood specimen in a blue top tube containing sodium citrate.

D. Recollect the blood specimen in a blue top tube containing sodium citrate. Feedback If either platelet satellitism or platelet clumps are observed on the peripheral smear, the sample should be recollected using sodium citrate as the anticoagulant. Platelets can then be counted using the automated method. The platelet count from a tube that contains liquid sodium citrate will need to be corrected for the dilutional effect of the citrate; this can be accomplished by multiplying the platelet count obtained from the automated analyzer by 1.1. Any suggested remedy involving EDTA as the anticoagulant will not be effective because the presence of EDTA is causing the satellitism to occur. Refrigeration will not disperse the platelet satellitism or platelet clumping for an accurate platelet count.

What does thrombocytopenia result from?

Deficient platelet production Abnormal platelet distribution Increased destruction