Testing of Primary Hemostasis

Question 1

What temp is testing performed at?

Answer 1

37 Celsius

Question 2

What is the specimen of choice?

Answer 2

Plasma

Question 3

What is the anticoagulant used?

Answer 3

Sodium citrate

Question 4

What is the ratio of blood to anticoagulant?

Answer 4

9:1

Question 5

Why do most tests require the addition of calcium?

Answer 5

Because sodium citrate binds the calcium in plasma

Question 6

What is platelet poor plasma? (PPP)

Answer 6

Plasma containing less than 10 x 10^9/L platelets

Question 7

What is platelet rich plasma? (PRP)

Answer 7

Plasma containing approximately 200-300 x 10^9/L platelets

Question 8

Coagulation samples should be collected……?

Answer 8

First or immediately after a non additive tube

Question 9

Specimen Problems with Platelet Counts and Estimates

Answer 9

Clumping:
Capillary puncture or antibodies
Satellitism:
Caused  by EDTA
Giant platelets:
Counted as WBCs, Falsely lower plt count
Fragments RBCs:
Counted as plts, Falsely higher plt count

Question 10

Platelet Aggregation Studies

Answer 10

Test determines plts interacting with other plts when stimulated by plt agonists.

Question 11

Platelet Aggregation Studies

(Agonists)

Answer 11

ADP
Collagen
Ristocetin: depends of vWF
Epinephrine
Arachidonic acid: screening pt's for aspirin

Question 12

Platelet Aggregation Studies

(Primary Wave)

Answer 12

Represents direct response of plts to aggregating reagent; plt shape change and formation of small aggregates

Question 13

Platelet Aggregation Studies

(Secondary Wave)

Answer 13

Complete aggregation; endogenous ADP is released from the activated plt dense bodies

Question 14

Platelet aggregation Studies

(Methods)

Answer 14

Performed on aggregometer
Platelet Rich Plasma is used
*Aspirin inhibits plt aggregation

Question 15

Bleeding Time

3 Types

Answer 15

Duke
Ivy
Template

Question 16

Bleeding Time

Template

Answer 16

Prolonged with aspirin and other drugs
Standardized
BP cuff used
site is below inner aspect of elbow

Question 17

Bleeding Time

Range

Answer 17

1-9 minutes

Question 18

Bleeding Time Controversies

Answer 18

Will be prolonged if pt has low plt count, decreased fibrinogen, or vascular disease.
Not very sensitive.
Plt function can be decreased by drugs and foods (aspirin and onions).
Many surgeons no longer rely on this.

Question 19

Bleeding Time Compromises

Answer 19

Poor circulation at puncture site.
Disturbance of plt plug formation during blotting.
Excessive movement by pts.
Performing incision over scars, bruises.
Thick hair growth at puncture site.

Question 20

When should bleeding time not be performed?

Answer 20

If plt count less than 100,000 x 10^9/L

Question 21

Platelet Function Analyzer (PFA)

Answer 21

Specimen must be at room temp. and testing should be done within 2 hours.
Pumps whole blood (in citrate) through each of 2 apertures containing either:
Collagen/epinephrine (CEPI)
Collagen/adenosine diphosphate (CADP)
Instrument measures the time necessary for plts to occlude the aperture.
About 175 sec
Time to occlude the aperture is a function of plt count, plt activity, vWF activity, and hct.

Question 22

CEPI abnormal

CADP normal

Answer 22

Aspirin effect if probable

Question 23

CEPI abnormal

CADP abnormal

Answer 23

True plt functional disorder is probable

Question 24

Flow Cytometry

Answer 24

Development of antibodies reactive with plt surface receptors.
Useful for GPIb/IX deficiency (Bernard-Soulier) and GPIIIb/IIIa deficiency (Glanzmann’s thrombasthenia)