Common Tests for primary hemostasis

Question 1

Reasons platelets are hard to count

Answer 1

Adhere to foreign surfaces, easily disintegrate, hard to differentiate from debris, unevenly distributed due to clumping

Question 2

Normal platelet count (general)

Answer 2

150 to 450 x 10^9/L

Question 3

Platelet count decrease after 65 years

Answer 3

122 to 350 x 10^9/L in men, 140 to 379 x 10^9/L in women

Question 4

Platelet count < 100,000/µL

Answer 4

Most common cause of clinically important bleeding

Question 5

Phase-contrast microscope method reference

Answer 5

Described by Brecher and Cronkite

Question 6

EDTA whole blood dilution for phase-contrast

Answer 6

1:100 with 1% ammonium oxalate to lyse RBCs

Question 7

Platelets counted in phase-contrast method

Answer 7

25 small squares of central large square (1 mm²) in hemocytometer

Question 8

Verification of manual thrombocyte count

Answer 8

Estimate on Wright-stained PBS made from same specimen

Question 9

Alternate method to count platelets

Answer 9

Light microscope, but harder to visualize platelets

Question 10

Reference method for platelet count

Answer 10

Phase-contrast microscope method by Brecher and Cronkite

Question 11

Dilution for phase-contrast method

Answer 11

1:100 with 1% ammonium oxalate (lyses nonnucleated RBCs)

Question 12

Area for platelet count in hemocytometer

Answer 12

25 small squares of the central large square (1 mm²)

Question 13

Accuracy verification for manual count

Answer 13

Estimate on Wright-stained PBS from the same specimen

Question 14

Alternate method for platelet visualization

Answer 14

Light microscope (more difficult to visualize platelets)

Question 15

Platelet characteristics under phase-contrast microscopy

Answer 15

Diameter: 2-4 µm, Shape: round/oval, Color: light purple sheen

Question 16

Background feature often seen in phase-contrast microscopy

Answer 16

Ghost erythrocytes

Question 17

Counting area for platelets in hemocytometer

Answer 17

25 small squares of the central large square (1 mm²)

Question 18

Acceptable difference in counts between sides of hemocytometer

Answer 18

< 10% difference

Question 19

Action for uneven platelet distribution

Answer 19

Repeat the procedure if > 10% difference

Question 20

Anticoagulant used for phase-contrast platelet count

Answer 20

1% ammonium oxalate

Question 21

Purpose of placing charged hemocytometer in a moist chamber

Answer 21

Allows platelets to settle

Question 22

Components of a moist chamber

Answer 22

Damp filter paper in a Petri dish, applicator stick as support

Question 23

Incubation time for platelets in the moist chamber

Answer 23

15 minutes

Question 24

Formula for percentage difference

Answer 24

[(V1 - V2) / (V1 + V2 ) x 100]

Question 25

General formula for manual cell counts (average of platelet count should be counted on two sides)

Answer 25

PLT count (cells/µL) = (cells counted x dilution factor) / (area (mm²) x depth (0.1))

Question 26

Examine the thin area where

Answer 26

a few RBCs slightly overlap under oil immersion.

Question 27

Normal platelet count per 100x field on a wedge smear

Answer 27

Approximately 7 to 21 platelets.

Question 28

Platelet estimation formula

Answer 28

Average platelets/OIF x 20,000 = estimated platelet count (µL).

Question 29

Adjusted platelet estimation formula

Answer 29

(Average platelets per field x total RBC count) / 200 RBCs per field.

Question 30

Topic

Answer 30

Details

Question 31

200 in adjusted formula represents

Answer 31

Average RBCs per oil immersion field in the optimal assessment area.

Question 32

Platelet estimate of 0 to 49,000/µL; qualitative report

Answer 32

marked decrease

Question 33

Platelet estimate of 50,000 to 99,000/µL; qualitative report

Answer 33

moderate decrease

Question 34

Platelet estimate of 100,000 to 149,000/µL; qualitative report

Answer 34

slight decrease

Question 35

Platelet estimate of 150,000 to 199,000/µL; qualitative report

Answer 35

low normal

Question 36

Platelet estimate of 200,000 to 400,000/µL; qualitative report

Answer 36

normal

Question 37

Platelet estimate of 401,000 to 599,000/µL; qualitative report

Answer 37

slight increase

Question 38

Platelet estimate of 600,000 to 800,000/µL; qualitative report

Answer 38

moderate increase

Question 39

Platelet estimate above 800,000/µL; qualitative report

Answer 39

marked increase

Question 40

Designed to test platelet-rich plasma (PRP)

Answer 40

light-transmittance (optical) platelet aggregometry

Question 41

Centrifuge requirement for PRP

Answer 41

50 x g for 30 minutes

Question 42

PRP specimen storage

Answer 42

18 to 24°C until test

Question 43

PRP aggregometry initiation

Answer 43

No less than 30 minutes, within 4 hours

Question 44

Minimum whole blood volume needed for adequate PRP

Answer 44

9 to 12 mL

Question 45

Light-transmittance aggregometry is unreliable when whole-blood platelet count is

Answer 45

< 100,000/µL

Question 46

PRP amount with a platelet count of

Answer 46

200,000 to 300,000/µL

Question 47

Aggregating reagents ACE

Answer 47

ADP, Collagen, Epinephrine/adrenaline

Question 48

Normal response to ACE

Answer 48

BSS and vWF disease

Question 49

Abnormal response to ACE

Answer 49

Glanzmann's thrombasthenia

Question 50

Ristocetin normal response

Answer 50

Glanzmann's thrombasthenia

Question 51

Ristocetin abnormal response

Answer 51

BSS and vWF

Question 52

Measures platelet aggregation and ATP release (from dense granules)

Answer 52

Platelet lumiaggregometry

Question 53

Specimen for platelet lumiaggregometry

Answer 53

Whole blood diluted with saline

Question 54

Reagent for platelet lumiaggregometry

Answer 54

Luciferin-luciferase

Question 55

Source of luciferin-luciferase

Answer 55

Firefly