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MLT Ch3 Hemostasis
Flashcards made directly from the Success! in Clinical Laboratory Science book
| Question | Answer |
|---|---|
| the hemorrhagic problems associated with scurvy are due to a deficiency of ___?___, which if a cofactor required for collagen synthesis | Vitamin C |
| The number of platelets an average megakaryocyte generates is approximately | 2000-4000 |
| what are some causes of thrombocytopenia | splenomegaly, chemotherapy, aplastic anemia |
| platelets interacting with and binding to other platelets is referred to as | aggregation |
| in platelet aggregation studied, certain aggregation agents induce a biphasic aggregation curve. This second phase of aggregation is directly related to | formation of fibrin |
| a platelet aggregation agent that characteristically yields a biphasic curve when used in optimal concentration is | epinephrine |
| the operating principle of a platelet aggregometer is best described as | change in optical density: as platelets aggregate, the optical density of the platelet-rich plasma decreases |
| of the following therapeutic agents, those considered to be antiplatelet medications are; aspirin and plavix, coumadin and heparin, heparin and protamine sulfate, tissue plasminogen activator and streptokinase | aspirin and plavix |
| a potent inhibitor of platelet aggregation released by endothelial cells is | prostacyclin |
| the reference value for mean platelet volume (MPV) is approximately | 8-10 fL |
| the platelet parameter PDW refers to the | variation in platelet cell size |
| a normal histogram showing platelet size distribution is best described as | right-skewed single peak |
| which of the following is not a normal maturation stage for platelets? megakaryoblast; promegakaryocyte; micromegakaryocyte; megakaryocyte | micromegakaryocyte |
| the recommended type of microscopy for the performance of manual platelet counts is | phase contrast |
| twenty microliters of blood are diluted in 1.98 mL of diluent. This dilution is plated on both sides of a Neubauer-ruled counting chamber.A total of 356 cells is seen when both large center squares are counted. The platelet count expressed in SI units is | 178X10^9/L - (total# of cells*dilution factor)/(total area counted*depth) so (356*100)/(2 mm^2*0.10mm)=178000=178X10^3/mm^3 when expressed in SI units the pllatelet count is 178X10^9/L |
| the size threshold range used by electrical impedance methods to count particles as platelets is | 2-20 fL |
| in storage pool disease, platelets are primarily deficient in | ADP |
| the anticoagulant required for routine coagulation testing is | sodium citrate |
| which of the following is not synthesized in the liver? Factor VIII, Plasminogen, Protein C, von Willebrand factor | von Willebrand factor |
| when thrombin binds to thrombomodulin on the endothelial cell surface, thrombin can | activate the protein C pathway |
| The coagulation factors having a sex-linked recessive inheritance pattern are | Factor VIII factor IX |
| prekallikrein deficiency is associated with | increased risk of thrombosis |
| which of the following will not cause the thrombin time to be prolonged? fibrin degradation products, heparin, factor I deficiency, factor II deficiency | factor II deficiency |
| the expected screening test results for a patient with a fibrin stabilizing factor deficiency are | normal prothrombin time and activated partial thromboplastin time |
| a patient on therapeutic warfarin will most likely have a(n) | increased PT/INR, increased aPTT, normal bleeding time, noral platelet count |
| what complexes are needed for blood coagulation to occur | VIIa, tissue factor Ca2+, IXa, VIII, PF3, Xa, V |
| con Willebrand factor is a | plasma protein that binds platelets to exposed subendothelial collagen |
| fibrin strands are cross-linked and the fibrin clot is stabilized by the activity of | factor XIIIa |
| which of the following enzymatically degrades the stabilized fibrin clot? plasminogen, plasmin, prothrombin, thrombin | plasmin |
| the activity of the lupus anticoagulant and anticardiolipin antibodies appears to be directed against | phospholipid |
| heparin inhibits clotting by | enhancing the action of antithrombin |
| the main regulatory protein of secondary hemostasis is | antithrombin |
| why is the activated partial thromboplastin time (aPTT) not the procedure of choice for detecting a platelet factor 3 (PF3) deficiency | the reagent contains a phospholipid substitute for PF3 |
| measurement of the time required for fibrin formation when thrombin is added to plasma evaluates the | fibrinogen concentration |
| a prolonged aPPT result is obtained on a patient diagnosed with acute disseminated intravascular coagulation (DIC). the patient has not yet been treated for this disorder. The most likely cause of the prolonged aPTT is | systemic activation of the coagulation system depletes some factors more rapidly than the liver can synthesize them |
| what are some characteristics of DIC | decreased fibrinogen concentration, positive test for degradation products, decreased platelet count |
| the principle of___?___ methods depends on cleavage of synthetic substrates by an active serine protease | chromogenic |
| epsilon aminocaproic acid is the treatment of choice for | primary fibrinogenolysis |
| a clot retraction defect is most likely due to | lack of platelet receptor glycoprotein IIb/IIIa |
| thrombocytosis is a characteristic of | polycythemia vera |
| in what functions are the products released by vascular endothelial cells involved | inhibition of platelet aggregation, activation of the fibrinolytic system, conversion of thrombin from a procoagulant to ananticoagulant |
| if a physician suspects a qualitative platelet defect, the most useful test to order is the | bleeding time |
| the coagulation factors referred to as "vitamin K-dependent" are | II,VII,IX,X |
| a patient on warfarin therapy will be deficient in a functional amount of | protein C and protein S |
| A 25- year old male presents to his physician complaining of leg pain. the physician diagnoses a deep vein thrombosis and wants to determine the cause of the thrombotic episode what could be associated with such a throbotic episode | Factor V Leiden and Prothrombin 20210 mutations, Lupus anticoagulant and anticardiolipin antibodies, and antithrombin and protein C deficiencies |
| and 85 year old male with slurred speech and paralysis on teh right side of the body is seen in the emergency department. A stat D-dimer is ordered and is very high. the doctor suspects a thromboembolic even. what is the most likely diagnosis/therapy | stroke; treat with tissue plasminogen activator |
| reversal of a heparin overdose can be achieved by administration of | protamine sulfate |
| what describes protein C | Vitamin K- dependent inhibitor to clotting |
| the prothrombin time will detect deficiencies in the ___?___ pathway(s) when calcium and a tissue factor source such as rabbit brain are added to plasma | extrinsic and common |
| a 65 year old patient in the emergency department has a normal d-dimer and an elevated FDP result. these results are consistent with the presence of degradation consistent with the presence of degradation products of | fibrinogen |
| a specimen is received for a prothrombin time and activated partial thromboplastin time. The 5mL tube has 2.5mL of blood in it. Expected test results are | PT and a PTT both falsely long |
| a microtainer EDTA sample is gotten from a fingerstick. It is run on an automated cell counter. platelet results are 178X10^9/L. the stained smear shows an average of 9 platelets per field under 1000X magnification. Based on this data you should | report the results because the platelet count and platelet estimate correlate |
| A 3 year old had an aPTT drawn. He had to be restrained by several people to have the venipuncture. The result of the child's aPTT was 18.0 sec (ref range 22.0-38.0 sec). The aPTT controls were in range. What would account for the low aPTT result? | the aPTT is invalid because of contamination with tissue factor |
| A surgical patient is having a pre-op CBC with platelet count.The automated platelet count is 57X10^9/L.The smear shows approx. 12 platelets on 1000X mag,, many of which are encircling neutrophils.Controls are in range.What is the best course of action | have the specimen redrawn using 3.2% sodium citrate as the anticoagulant |
| a phlebotomist drew a patient's blood for an aPTT at 10AM, but didn't bring it to the laboratory for testing until 4:30PM for testing. what would be the expected result? | a falsely long aPTT is expected because some factors deteriorate rapidly at room temperature |
| An aPTT and PT are ordered for a patient. On an optical density clot detection system, controls are within range. The results exceed the upper limit of linearity. The plasma is grossly lipemic, but there is enough to repeat tests. what should you do? | Repeat the aPTT and PT on an instrument that detects clot formation electromechanically |
| A sodium citrate tube is received in the lab for a PT and aPTT testing. results are: PT >100.0 seconds; aPTT >200.0 sec. on examination, a large clot is discovered. the abnormal test results are due to deficiencies of factors | I, II, V, VIII,XIII |
| a 30 year old female is admitted to the hospital with neurological symptoms.The following results are obtained:hemoglobin - 60g/L, hematocrit 0.19 L/L, platelet count 25X10^9/L, RBC morph - many schistocytes, ADAMTS-13 - markedly decreased. Diagnosis is? | thrombotic thrombocytopenic purpura |
Created by:
Mwortman
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