Section 8

Question 1

Specimen collection

Answer 1

3.2% sodium citrate (light blue top tube)
EDTA - degrades Factor V
Heparin - inhibits coag factors
Binds Ca

Question 2

Specimen adjustment

Answer 2

More Hct - less anticoagulant
Less Hct - More anticoag

Question 3

Sample centrifugation

Answer 3

Coag uses PPP
Platelet uses PRP

Question 4

Specimen handling

Answer 4

Always in plastic - glass has activating factors
for PT - RT for up to 24 hours
for APTT - up to 4 hours

Question 5

Mechanical Coag instrumentation

Answer 5

Electromechanical: two probes. Circuit connected with clot formation
Magnetically: Detects movement change in small steel ball

Question 6

Photoptical coag instruments

Answer 6

Turbometric: decrease in detection of light as clot forms
Nephelometric: Antigen-antibody complexes precip causing turbidity that scatters light. measures scattered like at 90 and 180 degree angles.

Trouble with turbidity of the sample

Question 7

Prothrombin Time

Answer 7

Extrinsic Pthwy
VII
uses PPP
Reagent: thromboplastin
Does NOT test for factor XIII

Question 8

Thromboplastin

Answer 8

Reagent in PT
Includes TF3
Phospholipid *PF3 replacement
CaCL to overcome the sodium citrate

Question 9

PT reference range

Answer 9

11-13 seconds

Question 10

International Normalized Ratio

Answer 10

PIVKA - proteins made by Vit K absence of antogonists
Reagent sensitivity to PIVKAs determines INR

Question 11

International sensitivity index

Answer 11

ISI- baseline 1, further from 1 the reagent for PT is the more sensitive it is to PIVKAs

Question 12

INR calculation

Answer 12

INR = (Patient PT/Normal PT)^ISI

RR: .9-1.2

Question 13

Activated Partial Thromboplastin Time

Answer 13

Intrinsic Pathway
VIII, IX, X, XI, XII, PK, HMWK
Uses PPP
2 reagents: Activator and CaCL

RR: 26-36 seconds

Question 14

APTT reagents

Answer 14

IX,XI, PK, HMWK
Contact activators
Phospholipids

Question 15

APTT use

Answer 15

Monitors effects of Heparin

Question 16

PT use

Answer 16

Monitors oral anticoag effects

Question 17

Approach to bleeding disorders

Answer 17

PT normal/APTT prolonged: XII,XI,IX,VIII,PK,HMWK
PT prolonged/APTT normal: VII
PT & APTT Prolonged: X, V, II, I

Assuming a single factor defficiency

Question 18

Thrombin Time

Answer 18

Tests for adequacy of fibrinogen
I -> Ia
Reagent: dilute Thrombin

RR: 14-20 seconds

Question 19

50:50 mix

Answer 19

Determines if prolonged PT/APTT/TT is due to a factor deficiency or an inhibitor

Question 20

50:50 mix results

Answer 20

Addition of normal plasma corrects towards the RR: factor deficiency
Addition of normal plasma has no effect: inhibitor

Question 21

Fibrinogen assays

Answer 21

Immunological: Measures AG (total fibrinogen, even dysfunctional)
Fibrinogen activity: most common. Measures functional Fibrinogen

Question 22

Fibrinogen assay vs TT

Answer 22

Fibrinogen uses 1:10 diluted plasma. minimizes inhibitors
reported as a standard curve vice a time in seconds.

Question 23

Fibrinogen reagents

Answer 23

Calibrating reference
thrombin
Owrens veronal buffer

Question 24

D-Dimers

Answer 24

formed in the process of 2nd degree fibrinolysis
Assays use monoclonal Abs, most commonly in latex agglutination

Question 25

D-Dimer assay interpretation

Answer 25

D-Dimers present in fibrinolysis -> active thrombosis (DIC, DVT, PE)
Watch out for post zone phenomenon

Question 26

RVVT

Answer 26

Russell Viper Venom Time
Activator of factor X. Ca and patient PPP tests common pthwy
RR: 20-30 seconds

Question 27

Reptilase Time

Answer 27

RT
Acts same as thrombin on Fibrogen, excepts only cleaves A
Not inhibited by common inhibitors (heparin/anticoags)
FDP will inhibit but to a lesser degree

Question 28

RT use

Answer 28

Differentiates lack of Fibrinogen from presence of inhibitor
RR: 16-22 seconds

Question 29

TT is prolonged/RT normal

Answer 29

Heparin inhibitor

Question 30

TT is prolong and RT is prolong

Answer 30

Inhibited by FDPs
Lack of fibrinogen

Question 31

Urea solubility

Answer 31

Determines adequacy of Factor XIII
RR: 60-150%