Reference Ranges & Test Principles Flashcards
OHSU Ranges
1
Q
Reference Range:
Prothrombin Time
A
11-13 seconds
2
Q
Reference Range:
PT w/ Oral Anticoagulants
A
20-27 seconds
Think 2x-ish the range values of normal
3
Q
Reference Range:
INR
A
0.9-1.2
4
Q
Reference Range:
INR Therapeutic Range
A
~2.0-3.0
5
Q
Reference Range:
APTT
A
26-36 seconds
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
7
Q
Reference Range:
Thrombin Time (TT)
A
14-20 seconds
8
Q
Reference Range:
Fibrinogen Assay
A
200-450 mg/dL
9
Q
Reference Range:
FDP Latex Agglutination
A
2-8 μg/mL
10
Q
Reference Range:
D-Dimer
A
<0.5 μg/mL (Negative)
11
Q
Reference Range:
Factor Assay Procedure
A
60-150%
12
Q
Reference Range:
Russell Viper Venom Time (RVVT)
A
20-30 seconds
13
Q
Reference Range:
Reptilase Time (RT)
A
16-22 seconds
14
Q
Reference Range:
Euglobulin Clot Lysis
A
Greater than 1 hour, usually <4 hours
15
Q
Reference Range:
Urea Clot Lysis (Urea Solubility)
A
Greater than 24hrs
*Shorter Test Name, Longer Reference Range Time (compared to Euglobulin)
16
Q
Reference Range:
Bleeding Time
A
2.5-9.5 minutes
17
Q
Reference Range:
TT
A
14-20 seconds
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
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
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.
21
Q
Interpretation
50:50 Mix
A
- Corrected Abnormal Result: Suspect Deficiency
- Uncorrected Abnormal Result: Suspect Inhibitor
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)
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
24
Q
Methodology
APTT Reagent(s)
A
Activator Reagent
* Contact Activator (Celite, Kaolin, Ellagic Acid, or Silica)
* Phospholipid (PF3 Substititute
CaCl2
25
# Methodology
PT Reagent(s)
Thromboplastin
* Tissue Factor 3
* Phospholipid (PF3 Substitute)
* CaCl2 (to override sodium citrate)
26
# Name & Principle
CTT
**Corrected Thrombin Time**
* 50:50 Mix for Prolonged TT to test for deficiency or inhibitors
27
# 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?
False - Affected factors are not decreased, but produced in incomplete form
* Affected Factors are the Magic Four
28
# Principle
D-Dimer
Tests for presence of polymerized D-dimers, polymerized fragments of the D domain held together by FXIII cross-linkage
29
# Principle
Factor Assay
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
# 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
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
# Methodology
What is consistent across all types of D-Dimer Immunoassays?
All assays use a monoclonal Ab
32
# Test Interpretation
What must be taken into consideration when reviewing D-Dimer assay results?
Post-zone phenomenon can occur
33
# Pathophysiology
In what instances will D-Dimers be positive?
Cases of active thrombosis
* DIC
* DVT
* PE
34
# True/False
D-Dimer and FDP are positive in primary fibrinolysis
False - D-Dimer is only positive in secondary fibrinolysis
| *Primary fibrinolysis is fibrinogen, no cross-linkages present yet
35
# Name & Principle
INR
**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
# Name & Principle
TT
**Thrombin Time**
* Tests for adequacy of **ONLY** Fibrinogen
| The test name we love to hate - Thrombin is added, not measured
37
# Methodology
TT Reagent(s)
Dilute Thrombin
38
# Result Interpretation
Urea Clot Lysis
Adequate FXIII Activity: Clot Remains
Inadequate FXIII Activity: Clot Lysis
39
# Name & Principle
Define PIVKA and how they relate to INR
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
# Name & Principle
INR Equation
INR = (Patient PT/Normal PT)^ISI
41
# Testing
Corresponding Lab Tests for Coumadin Therapy
PT & INR
42
# Testing
Corresponding Lab Tests for Heparin Therapy
APTT
43
# Methodology
Types of Fibrinogen Assays
* Immunological Fibrinogen
* Fibrinogen Activity
44
# Principle
Immunological Fibrinogen
**Measures Fibrinogen Ag**
* Quantitates total fibrinogen (even dysfunctional)
* RID Method
* Nephelometry
45
# Principle
Fibrinogen Activity
**Most commonly performed fibrinogen assay**
* Quantitates only functional fibrinogen
* Mechanical or photo-optic method
46
# Principle
List the differences between TT and Fibrinogen Activity
* 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
# Methodology
Fibrinogen Assay Reagents
* Fibrinogen Calibration Reference
* Thrombin (much stronger variety than used in TT)
* Owrens Veronal Buffer as Diluent
48
# Result Interpretation
When will FDPs be positive?
In both primary and secondary fibrinolysis
49
# Name & Principle
FDP
**Fibrin and/or Fibrinogen Degradation Products (FDP)**
* Semi-quantitative measure of FDPs
50
# Principle
What must be kept in mind with FDP interpretations?
Post-zone Phenomenon
51
# Testing
What is the clinical purpose of an Anti-Xa Assay?
Monitor therapy with Low Molecular Weight Heparin (LMWH), Unfractionated Heparin (UFH), or Direct Factor Xa Inhibitors
52
# Test Principle
Anti-Xa Assay
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
# 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.
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
# Name & Principle
RVVT
**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
# Name & Principle
RT
**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
# Test Principle
What interfering substance can inhibit RT?
FDPs (but to a lesser degree than TT)
57
# T/F
Factor XIII adequacy can be measured via other methods than Urea Clot Lysis testing.
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
# Clinical Utilization
Euglobulin Clot Lysis
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
