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Hematology > Coag Rotation Quiz 1 > Flashcards

Coag Rotation Quiz 1 Flashcards

1
Q

How does sodium citrate inhibit coagulation?

A

sodium citrate prevents the specimen from clotting by removing ionic calcium from the blood by chemical binding

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2
Q

State the optimum blood: anticoagulant ratio

A

9:1 blood to anticoagulant ration

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3
Q

How will a patient with polycythemia affect coag test results?

A

will contain too little plasma, test results prolonged

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4
Q

How will a half-filled vacutainer on patient with a normal hematocrit affect coag test results?

A

ratio of blood to anticoagulant is altered, and the test result may be incorrect

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5
Q

How will a patient with anemia (Hct=18%) affect coag test results?

A

no correction for anemia, test results normal

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6
Q

What is the effect of mild hemolysis on coag tests?

A

generally, not affect the results of coagulation testing

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7
Q

What is the effect of severe hemolysis on coag test?

A

Facts V and VIII are often decreased causing a prolongation in testing results
also, tissue thromboplastin can be released during drawing of a hemolyzed specimen causing micro-clots in the specimen

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8
Q

Why is sodium citrate the only suitable anticoagulant for coagulation studies?

A

it is the best anticoagulation to use as factors V and VIII are more stable in it than in other anticoagulants

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9
Q

What is the effect of a small clot on coagulation testing?

A

small clots in the specimen tube can prolong coag tests

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10
Q

What are the specimen integrity checks for coag samples?

A

check for clot, check fill volume of tube, check Hct<55%, tube labeled with 2 patient identifiers

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11
Q

What conditions could be responsible for an increased thrombin time?

A

presence of heparin
FDP
hypofibrinogenemia
decreased fibrinogen
dysfibrinogenemia
afibrinogenemia

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12
Q

What is the normal range for thrombin time at OSF?

A

15.1-18.5 seconds

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13
Q

Explain the role of the thrombin in maintaining hemostasis.

A

most important enzyme involved in thrombogenesis
responsible for conversion of fibrinogen to fibrin
involved in proteolytic process of activation of factors XII, XI, V, VIII, protein C and cleavage to TAFI and platelet PAR-1 receptor to maintain hemostasis
most sensitive and specific test for detecting residual heparin

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14
Q

Explain the principal of the PFA test

A

measures the time it takes for blood (in a high shear environment) to block a membrane coated with either collagen/epinephrine or collagen/ADP
replaces the bleeding time as a test of platelet function

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15
Q

How will ingestion of aspirin affect PFA 100 results?

A

aspirin inhibits the platelet enzyme, cyclo-oxygenase, which is necessary for production of thromboxane

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16
Q

What role do platelets play in hemostasis?

A

platelets are involved in primary hemostasis by adhesion to one another to stop bleeding via interaction between GPIb and von Willebrand factor

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17
Q

Normal PFA results

A

COL/EPI and ADP = normal

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18
Q

Patient taking aspirin PFA results

A

COL/EPI= Abnormal COL/ADP=normal

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19
Q

Patient with vWD PFA results

A

COL/EPI and ADP = Abnormal

20
Q

Patient with Glansman’s Thrombastenia PFA results

A

N=4, COL/EPI and ADP= Abnormal

21
Q

What is the clinical significance of an abnormal closure time?

A

patient could have either a congenital or acquired disorder of platelet function
prolonged times are found in thrombocytopenia and platelet dysfunction
the most common causes of plt dysfunction are related to uremia, vWD and exposure to agents such as acetyl salicylic acid (aspirin)

22
Q

List the coagulation factors and which coagulation pathways are tested for in the protime test

A

extrinsic or tissue factor pathwar: Factor VII
common pathway: Factor X. V. II (prothrombin) and I (fibrinogen)
three of four vitamin k-dependent proteins: Factor VII. X. II

23
Q

What factor is depleted most rapidly in the PT test system?

A

VII is depleted most rapidly in the PT system due to its short life

24
Q

What is the INR, and why is it used when reporting protime results?

A

international normalizing ratio, allows physicians to compare PT results from different institutions even though different methodologies and reagents are used

25
Q

What is the normal range for the PT at OSF-SFMC?

A

11.6-14.8

26
Q

List the coagulation factors and which coagulation pathways are tested for in the APTT test.

A

intrinsic pathway: XII, XI, IX, VII
common pathway: X, V, II, I

27
Q

What is the normal range for the APTT at OSF-SFMC?

A

24-36 seconds

28
Q

What medication is LMWH used to monitor?

A

low molecular weight heparin

29
Q

what test can be used to monitor for HIT in patients taking UFH?

A

heparin dependent (PF4) IgG antibody

30
Q

What steps should be taken to troubleshoot coag QC? Can patient samples be resulted if QC is out of range?

A

If you have a shift in QC, (abrupt change) look at what changed from the last time QC was run until present time. Were reagents changed? New QC put on?
If you have a trend in QC (QC has been drifting high or low) think about the condition
the instrument is in. Has shift maintenance been done?
Patient results are not reported until controls fall with accepted limits.

31
Q

Explain the principle of fibrinogen analysis.

A

Thrombin converts fibrinogen to fibrin. At high thrombin concentrations, the reaction rate is determined by the pt’s fibrinogen concentration. Results are calculated from a standard curve. The clotting time of diluted plasma is inversely proportional to the level of plasma fibrinogen.

32
Q

What is fibrinolysis, and how is it related to fibrin degradation products?

A

Fibrinolysis is the dissolution of fibrin by fibrinolysin, caused by the action of the proteolytic enzyme system. This system is continually active in the body but activity is greatly increased by various stress stimuli. Increased activity of the fibrinolytic system would result in an increased FDP. The formation of FDP occurs following plasmin digestion of either fibrinogen or fibrin. D-dimer is formed after plasmin degradation of fibrin.

33
Q

What is the normal range for fibrinogen at OSF-SFMC?

A

185-475mg/dl

34
Q

What is DIC? What are the expected D-Dimer values in DIC?

A

Disseminated intravascular coagulation is a condition where the normal hemostatic balance is altered, allowing uncontrolled, inappropriate formation of fibrin within blood vessels. As a result, coag factors and platelets are consumed, FDPs are formed and bleeding occurs at the same time disseminated clotting occurs. Both coagulation and fibrinolysis are occurring. FDP and D-Dimer values are increased in DIC. Data indicates that the D-dimer test is slightly more sensitive in detecting DIC than the FDP assay.

35
Q

Explain the principal and utilization of the Dimer test.

A

D-Dimer uses quatitative latex agglutination test in which antigen-antibody reaction takes place, resulting in absorbance change equivalent to the D-Dimer level present.
Test is of high significance for its negative predictive value, which aids in the exclusion of a diagnosis of DVT or PE.

36
Q

Which group of factors require Vitamin K?

A

Prothrombin Group: Factors II, VII, IX. X

37
Q

Which group of factor are involved in the initial activation of the intrinsic pathway and require contact with a negatively charged surface for activation?

A

Contact Group: Factors XII, XI, Pre-kallikrein, HMWK

38
Q

Which group of factors are consumed during clotting?

A

Fibrinogen Group: Factors I, V, VIII, XIII

39
Q

Why are controls used in coagulation testing?

A

A control plasma is used to monitor performance of lab test system- reagents, instruments, reconstitution of fluids, pipes, etc.

40
Q

Why do different institutions have different normal ranges for the same tests?

A

normal ranges vary from one institution to another because of different reagents different lot #s, different instrumentation, and different patient populations

41
Q

How does a normal range differ from a normal control?

A

a normal range is a clinical term used to make a clinical interpretation. a normal range is established by each institution based upon testing of multiple normal individuals
a normal control is established by either the commercial control or the institution by repeated testing of the same control, the control range and pt ranges may be similar but not necessarily identical

42
Q

List 6 sources of error in performing coagulation tests.

A

measuring devices (pipets, automatic diluters)
timing devices (incorrect incubation)
contamination (bacteria, heparin)
blood samples (incorrect drawing, specimen storage, high/low Hct)
temperature of test reaction
different lot # of reagents

43
Q

Explain how heparin therapy would affect the PTs and PTTs.

A

Heparin will prolong both the PT and PTT. Heparin inhibits thrombin, factors Xa, IXa and XIIa.

44
Q

List the factors affected by coumadin (oral coagulants).

A

IX, X, VII and prothrombin. Coumadin acts as a vitamin K antagonist. These are also
the factors found in the prothrombin complex

45
Q

Why is the PT test the best way to monitor coumadin therapy?

A

The PT tests for factor VII. VII has the shortest half life so any prolongation of clot formation will first be noted in the PT.

46
Q

What is the prothrombin complex?

A

A commercial preparation that contains prothrombin, VII, IX, X (vitamin K dependent factors).

47
Q

Describe the mechanism for type II heparin-induced thrombocytopenia.

A

This is an immune disorder with severe thrombocytopenia. The onset is slow (8 days average) and very symptomatic. Heparin binds to proteins on the platelet surface. Antibodies to the platelet-heparin complex bind to antigens on the heparin molecule. Immune complexes are formed that bind to receptors on the platelet surface, resulting in platelet activation. This leads to aggregation, release and recruitment, resulting in thrombocytopenia.

Hematology (3 decks)

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