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Hemostasis Exam III - Going Pro(thrombin) > Reference Ranges & Test Principles > Flashcards

Reference Ranges & Test Principles Flashcards

OHSU Ranges

1
Q

Reference Range:

Prothrombin Time

A

11-13 seconds

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2
Q

Reference Range:

PT w/ Oral Anticoagulants

A

20-27 seconds

Think 2x-ish the range values of normal

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3
Q

Reference Range:

INR

A

0.9-1.2

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4
Q

Reference Range:

INR Therapeutic Range

A

~2.0-3.0

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5
Q

Reference Range:

APTT

A

26-36 seconds

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6
Q

Reference Range:

APTT w/ Heparin

A

1.5-2.5x Patient Normal APTT Range
(possible range of 39-54 sec to 65-90 sec)

Same as PT with thinking ~2x range of values

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7
Q

Reference Range:

Thrombin Time (TT)

A

14-20 seconds

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8
Q

Reference Range:

Fibrinogen Assay

A

200-450 mg/dL

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9
Q

Reference Range:

FDP Latex Agglutination

A

2-8 μg/mL

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10
Q

Reference Range:

D-Dimer

A

<0.5 μg/mL (Negative)

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11
Q

Reference Range:

Factor Assay Procedure

A

60-150%

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12
Q

Reference Range:

Russell Viper Venom Time (RVVT)

A

20-30 seconds

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13
Q

Reference Range:

Reptilase Time (RT)

A

16-22 seconds

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14
Q

Reference Range:

Euglobulin Clot Lysis

A

Greater than 1 hour, usually <4 hours

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15
Q

Reference Range:

Urea Clot Lysis (Urea Solubility)

A

Greater than 24hrs

*Shorter Test Name, Longer Reference Range Time (compared to Euglobulin)

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16
Q

Reference Range:

Bleeding Time

A

2.5-9.5 minutes

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17
Q

Reference Range:

TT

A

14-20 seconds

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18
Q

Name & Principle

PT

A

Prothrombin Time
* Measures adequacy of Extrinsic Pathway (specifically Factors VII, X, V, II, and I
* Used to monitor effects of anticoagulants

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19
Q

Principle

What does PT not test for?

A
  • Factor XIII
  • TF-III, Ca2+, or PF3
  • Insensitive to alternative pathway activation of FIX via FVIIa
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20
Q

Principle

50:50 Mix

A
  • If one of the coag screening tests (PT, APTT, TT) is prolonged, determines if abnormality is due to a deficiency or an inhibitor.
  • Determined by mixing normal plasma and patient plasma in a 1:1 ratio & repeating the abnormal test.
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21
Q

Interpretation

50:50 Mix

A
  • Corrected Abnormal Result: Suspect Deficiency
  • Uncorrected Abnormal Result: Suspect Inhibitor
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22
Q

Methodology

What are the substances used in a PT procedure and how are they prepped?

A

Thromboplastin & PPP (both separately warmed to 37°C)

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23
Q

Name & Principle

APTT

A

**Activated Partial Thromboplastin Time (APTT) **
* Measures adequacy of Intrinsic Pathway
* Tests for adequacy of Factors XII, XI, IX, VIII, X, V, II, I, PK, and HMWK
* Used to monitor effects of Heparin

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24
Q

Methodology

APTT Reagent(s)

A

Activator Reagent
* Contact Activator (Celite, Kaolin, Ellagic Acid, or Silica)
* Phospholipid (PF3 Substititute

CaCl2

25
Q

Methodology

PT Reagent(s)

A

Thromboplastin
* Tissue Factor 3
* Phospholipid (PF3 Substitute)
* CaCl2 (to override sodium citrate)

26
Q

Name & Principle

CTT

A

Corrected Thrombin Time
* 50:50 Mix for Prolonged TT to test for deficiency or inhibitors

27
Q

True/False

When a patient is placed on oral anticoagulant therapy, the affected factors are decreased in concentration.

Additional Question: What are the factors affected by this therapy?

A

False - Affected factors are not decreased, but produced in incomplete form
* Affected Factors are the Magic Four

28
Q

Principle

D-Dimer

A

Tests for presence of polymerized D-dimers, polymerized fragments of the D domain held together by FXIII cross-linkage

29
Q

Principle

Factor Assay

A

Reruns abnormal test (PT/APTT), utilizing specific factor deficient plasma as a reagent to determine if patient is deficient in the suspected factor.
* Multiple test runs with a series of dilutions utilizing the deficient plasma can then be used to create a standard curve to determine patient % activity of a specific factor

Ex: Pt. Plasma + FVIII Deficient Plasma = Factor Assay for FVIII

30
Q

Result interpretation

If a patient is suspected to have Hemophilia B, how would you interpret these results?

PT - 11 sec
APTT - 56 sec
50:50 APTT - 39 sec
50:50 APTT rerun with FIX Deficient Plasma - 36 sec

A

Patient does not have a FIX deficiency as suspected, 50:50 APTT with Factor IX Deficient Plasma showed corrected values
* FIX Deficient Plasma added a different factor that was missing from the patient sample due to the unknown deficiency
* In this instance, if multiple dilutions were performed and a standard curve made, the % activity of FIX would be within normal limits.

31
Q

Methodology

What is consistent across all types of D-Dimer Immunoassays?

A

All assays use a monoclonal Ab

32
Q

Test Interpretation

What must be taken into consideration when reviewing D-Dimer assay results?

A

Post-zone phenomenon can occur

33
Q

Pathophysiology

In what instances will D-Dimers be positive?

A

Cases of active thrombosis
* DIC
* DVT
* PE

34
Q

True/False

D-Dimer and FDP are positive in primary fibrinolysis

A

False - D-Dimer is only positive in secondary fibrinolysis

*Primary fibrinolysis is fibrinogen, no cross-linkages present yet

35
Q

Name & Principle

INR

A

International Normalized Ratio
* This “correction” standardizes patient results between laboratories.
* When a patient is placed on oral anticoagulant therapy, the affected factors (magic 4) are not decreased in concentration, they are simply produced in an incomplete form.

36
Q

Name & Principle

TT

A

Thrombin Time
* Tests for adequacy of ONLY Fibrinogen

The test name we love to hate - Thrombin is added, not measured

37
Q

Methodology

TT Reagent(s)

A

Dilute Thrombin

38
Q

Result Interpretation

Urea Clot Lysis

A

Adequate FXIII Activity: Clot Remains
Inadequate FXIII Activity: Clot Lysis

39
Q

Name & Principle

Define PIVKA and how they relate to INR

A

PIVKA - Proteins Induced by Vitamin K Absence or Antagonists
* Can affect PT, amount of effect depends on sensitivity of reagent to presence of PIVKAs.
* Reagent Sensitivity is indicated by ISI which is used to calculate INR to correct the result and account for the varying reagents.

40
Q

Name & Principle

INR Equation

A

INR = (Patient PT/Normal PT)^ISI

41
Q

Testing

Corresponding Lab Tests for Coumadin Therapy

A

PT & INR

42
Q

Testing

Corresponding Lab Tests for Heparin Therapy

A

APTT

43
Q

Methodology

Types of Fibrinogen Assays

A
  • Immunological Fibrinogen
  • Fibrinogen Activity
44
Q

Principle

Immunological Fibrinogen

A

Measures Fibrinogen Ag
* Quantitates total fibrinogen (even dysfunctional)
* RID Method
* Nephelometry

45
Q

Principle

Fibrinogen Activity

A

Most commonly performed fibrinogen assay
* Quantitates only functional fibrinogen
* Mechanical or photo-optic method

46
Q

Principle

List the differences between TT and Fibrinogen Activity

A
  • Fibrinogen Activity performed on diluted 1:10 plasma to minimize effect of inhibitors (ie heparin)
  • Results not reported in seconds, uses standardized curve to convert clotting time to mg/dL of fibrinogen
47
Q

Methodology

Fibrinogen Assay Reagents

A
  • Fibrinogen Calibration Reference
  • Thrombin (much stronger variety than used in TT)
  • Owrens Veronal Buffer as Diluent
48
Q

Result Interpretation

When will FDPs be positive?

A

In both primary and secondary fibrinolysis

49
Q

Name & Principle

FDP

A

Fibrin and/or Fibrinogen Degradation Products (FDP)
* Semi-quantitative measure of FDPs

50
Q

Principle

What must be kept in mind with FDP interpretations?

A

Post-zone Phenomenon

51
Q

Testing

What is the clinical purpose of an Anti-Xa Assay?

A

Monitor therapy with Low Molecular Weight Heparin (LMWH), Unfractionated Heparin (UFH), or Direct Factor Xa Inhibitors

52
Q

Test Principle

Anti-Xa Assay

A
  1. Patient Plasma w Added Reagent that has a constant amount of FXa
    * Inhibition of FXa will occur proportional to antithrombotics present in patient plasma
  2. Chromogenic substrate is added
    * Any non-inhibited FXa remaining will cleave substrate and produce a color change
53
Q

True/False

The degree of color produced in an Anti-Xa Assay is directly proportional to the amount of antithrombotic agents present in the pateint sample.

A

False - The degree of color produced is inversely proportional to the amount of antithrombotics present
*Increased color = decreased antithrombotic present = less FXa inhibted and therefore more available to cleave the chromogenic substrate

54
Q

Name & Principle

RVVT

A

Russell Viper Venom Time (RVVT)
* Snake venom from Russell Pit Viper is a direct activator of FX
* Mixing venom with Ca2+ and patient PPP tests the common pathway

We don’t really worry about RVVT except for the Dilute test for LI -Dawn

55
Q

Name & Principle

RT

A

Reptilase Time (RT)
* Reptilase snake venom acts similarly to thrombin on fibrinogen. Only cleaves fibrinopeptide A though.
* Not inhibited by common thrombin inhibitors such as heparin or autoantibodies.
* Can be used to differentiate lack of fibrinogen from inhibitor presence.

56
Q

Test Principle

What interfering substance can inhibit RT?

A

FDPs (but to a lesser degree than TT)

57
Q

T/F

Factor XIII adequacy can be measured via other methods than Urea Clot Lysis testing.

A

True - Chromogenic & Antigenic methods (such as Latex Immunoturbidity or ElISA) can be used

Reference Range (%) in these cases is the same as other Factor Assays

58
Q

Clinical Utilization

Euglobulin Clot Lysis

A

Qualitative measure of patient’s endogenous Fibrinolytic Capability
* Often for monitoring fibrinolytic activity of patients on tPA, Streptokinase, or Urokinase therapy
* Useful in confirming patient isn’t being over-corrected by therapy and going through dangerous levels of fibrinogenolysis

59
Q
A

Hemostasis Exam III - Going Pro(thrombin) (3 decks)

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