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HEMATOLOGY 2 > COMMON TESTS FOR SECONDARY HEMOSTASIS > Flashcards

COMMON TESTS FOR SECONDARY HEMOSTASIS Flashcards

1
Q

Reagent for ‘partial’ in aPTT uses

A

phospholipid portion of tissue thromboplastin

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2
Q

aPTT reagent is derived from

A

brain or plant phospholipids

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3
Q

Primary improvement of aPTT over PTT

A

Complete contact activation by adding an activator, shortening PTT and narrowing the normal range

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4
Q

Examples of solid particulate activators used in aPTT

A

Silica, kaolin, celite, bentonite

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5
Q

Example of a soluble activator used in aPTT

A

Ellagic acid

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6
Q

Reference range for aPTT (general)

A

35 to 45 seconds

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7
Q

Specimen requirements for aPTT testing

A

Citrated platelet-poor plasma (<15,000/uL platelets) prepared by centrifugation

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8
Q

Components of the aPTT reagent

A

(1) Platelet substitute (phospholipid) and (2) Activator

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9
Q

Role of CaCl2 in aPTT testing

A

Re-calcifies the plasma to allow coagulation

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10
Q

Temperature requirement for aPTT testing

A

37°C (water bath)

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11
Q

Therapy monitored using aPTT

A

Unfractionated heparin (UFH) therapy

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12
Q

Pathways evaluated by aPTT

A

Intrinsic (VIII, IX, XI, XII) and common pathways (II, V, X, I)

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13
Q

Factors that can indicate coagulation deficiencies detected by aPTT

A

Common factors (II, V, X, I) and intrinsic pathway factors (VIII, IX, XI, XII)

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14
Q

Time for clotting to occur in aPTT test

A

Measured in seconds, reported to the nearest tenth

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15
Q

Component added after incubation in aPTT testing

A

Warmed CaCl2

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16
Q

Standard reference range for aPTT

A

35 to 45 seconds (generally)

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17
Q

Reference range for PT (generally)

A

10-13 seconds

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18
Q

Type of test for PT, aPTT

A

Clot-based coagulation screening test

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19
Q

Specimen requirements for PT testing

A

Citrated platelet-poor plasma (<15,000/uL platelets) prepared by centrifugation

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20
Q

Materials required for PT testing

A

Thromboplastin-Calcium Chloride (CaCl2) reagent (PT reagent; Simplastin)

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21
Q

Required equipment for PT testing

A

Test tubes (12 X 75-mm glass tubes), Pipets, 37°C water bath

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22
Q

Control material purpose in PT testing

A

Ensures validity and accuracy of test results

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23
Q

Primary use of PT

A

Monitors warfarin therapy

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24
Q

Pathways detected by PT

A

Common and extrinsic pathways

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25
Q

Procedure step in PT testing involving reagent temperature

A

Warm PT thromboplastin reagent at 37°C for 3 to 5 minutes

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26
Q

Volume of PT reagent added to plasma sample

A

0.2 mL of PT reagent to 0.1 mL of plasma

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27
Q

Unit for reporting PT results

A

Seconds

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28
Q

Alternative ways to report PT results

A

Patient time with control time, Patient time with reference range, Prothrombin ratio, INR

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29
Q

Purpose of INR (International Normalized Ratio)

A

Standardizes PT reporting to correct for variability in thromboplastin sensitivities

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30
Q

Calculation for prothrombin ratio

A

PT of patient divided by mean reference range, multiplied by 100

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31
Q

Key use of INR

A

Corrects for variability in PT results due to different thromboplastin agents

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32
Q

INR calculation requirement for Coumadin therapy

A

Calculated only for patients with a stable anticoagulation response

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33
Q

PT result interpretation during the first week of Coumadin therapy

A

Interpreted in seconds and compared with the reference interval

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34
Q

Target INR range for most indications

A

2.0 to 3.0

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35
Q

Target INR range for patients with a mechanical heart valve

A

2.5 to 3.5

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36
Q

Purpose of INR

A

Minimizes differences in PT results due to different reagent-instrument combinations

37
Q

Formula for calculating INR

A

Patients PT / Mean normal PT ^ ISI

38
Q

Definition of ISI in INR calculation

A

International Sensitivity Index

39
Q

Interpretation of ISI values for thromboplastin reagents

A

ISI < 1.0 for more sensitive reagents, ISI > 1.0 for less sensitive reagents

40
Q

Effect of more sensitive thromboplastin reagents on PT

A

Results in longer PT

41
Q

Effect of less sensitive thromboplastin reagents on PT

A

Results in shorter PT

42
Q

Coumarin drugs are Vitamin K antagonists (VKAs) that interfere with the synthesis of clotting factors

A

II, VII, IX, X, Proteins C and S

43
Q

Examples of coumarin drugs include dicumarol, phenprocoumon, acenocumarol, and the most commonly used drug

A

Warfarin

44
Q

Warfarin interferes with the synthesis of these clotting factors and proteins

A

Factors II, VII, IX, X, and Proteins C and S

45
Q

Reversal agents for warfarin overdose include

A

Vitamin K (oral/intravenous), Fresh-frozen plasma, Prothrombin complex concentrate, Recombinant activated factor VII (rVIIa)

46
Q

Forms of Vitamin K used to reverse warfarin overdose

A

Oral Vitamin K, Intravenous Vitamin K

47
Q

Options to reverse a warfarin overdose depending on patient condition

A

Vitamin K (oral/intravenous), Fresh-frozen plasma, Prothrombin complex concentrate, Recombinant activated factor VII (rVIIa)

48
Q

UFH acts as an anticoagulant by accelerating the binding of this protein to target enzymes

A

Antithrombin

49
Q

UFH is routinely used in this medical procedure

A

Cardiac surgery

50
Q

UFH therapy requires monitoring with these assays

A

Partial thromboplastin time (PTT), Activated clotting time (ACT)

51
Q

UFH is administered via this route

A

Intravenously

52
Q

Protamine sulfate neutralizes UFH. It is a protein extracted from this source

A

Fish sperm (salmon sperm)

53
Q

ACT (activated coagulation time) is an example of this type of test

A

Clot-based coagulation screening test

54
Q

ACT is a point-of-care assay used in these settings

A

Clinics, inpatient’s bedside, cardiac catheterization laboratory, surgical suite

55
Q

ACT is specifically useful in monitoring this aspect of UFH therapy

A

High UFH dosages

56
Q

ACT test procedure involves adding this to blood and recording the clotting interval

A

Particulate activator

57
Q

LMWH is produced by this process

A

Controlled fragmentation of heparin

58
Q

LMWH primarily inhibits this factor, but not thrombin

A

Activated factor Xa (factor Xa)

59
Q

LMWH is administered via this route

A

Subcutaneous injection

60
Q

LMWH has a lower incidence of this compared to unfractionated heparin

A

Heparin-induced thrombocytopenia

61
Q

LMWH has a lower incidence of these compared to unfractionated heparin

A

Hemorrhage, osteoporosis

62
Q

One disadvantage of LMWH compared to unfractionated heparin

A

Increased cost

63
Q

One disadvantage of LMWH compared to unfractionated heparin

A

More complicated monitoring

64
Q

Mechanical/Electromechanical examples of coagulation instrumentation

A

BBL fibrometer and Diagnostica Stago analyzers

65
Q

Uses electromechanical clot detection system that measures a change in conductivity between two metal electrodes in plasma

A

BBL fibrometer

66
Q

Uses the detection of the oscillation of a steel ball within the plasma-reagent solution. Viscosity starts to increase as fibrin strands form, slowing the movement

A

Diagnostica Stago analyzers

67
Q

Principle used in photo-optical coagulometers

A

Detects a change in plasma optical density during clotting

68
Q

Modification of photo-optical end-point detection used in nephelometric coagulometers

A

90-degree or forward-angle light scatter is measured instead of optical density

69
Q

Substrate used in chromogenic (amidolytic) coagulation assays

A

Synthetic oligopeptide conjugated to a chromophore, usually para-nitroaniline (pNA)

70
Q

Advantage of chromogenic assays in evaluating patients on anticoagulants or with inhibitors

A

Inhibitors do not interfere with the chromogenic assay

71
Q

Coagulation instrumentation based on antigen-antibody reactions

A

Immunologic coagulometers

72
Q

Russel’s viper venom function

A

Bypasses Factor VII and directly activates Factor X to Xa

73
Q

Stypven time use

A

Helps differentiate Factor VII and Factor X deficiencies

74
Q

Normal Stypven time value

A

20 to 25 seconds

75
Q

Dilute Russel’s Viper Venom Time (dRVVT) purpose

A

Detect lupus anticoagulants

76
Q

Normal dRVVT value

A

30 to 35 seconds

77
Q

Thrombin Time (TT) purpose

A

Detect low fibrinogen, impaired fibrinogen function, presence of heparin, fibrin(ogen) degradation products, and streptokinase

78
Q

Thrombin Time sensitivity

A

Sensitive in detecting heparin inhibition

79
Q

Normal Thrombin Time value

A

15 to 18 seconds

80
Q

Reptilase Time purpose

A

Converts fibrinogen to fibrin; unaffected by heparin

81
Q

Reptilase is an enzyme found in

A

Bothrops atrox snake

82
Q

Normal Reptilase Time value

A

10 to 15 seconds

83
Q

Thrombin Time and Reptilase Time in Hypofibrinogenemia

A

Both prolonged

84
Q

Thrombin Time and Reptilase Time in Immunologic Antithrombin

A

Thrombin time prolonged, Reptilase time normal

85
Q

Thrombin Time and Reptilase Time in Heparin Therapy

A

Thrombin time prolonged, Reptilase time normal

86
Q

Clotting Time Slide/Drop Method procedure

A

Perform skin puncture, transfer blood drop, check for fibrin strands every 30 secs

87
Q

Normal Clotting Time Slide/Drop Method value

A

2 to 4 minutes

88
Q

Normal Clotting Time Lee and White Method value

A

7 to 15 minutes

HEMATOLOGY 2 (15 decks)

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