Chapter 11: Manual, Semiautomated, and POCT

Question 1

Most common anticoagulant in routine hematology testing

Answer 1

Ethylenediaminetetraacetic acid (EDTA)

Question 2

Form of EDTA usually used in routine Hematology

Answer 2

K2EDTA

Question 3

How does EDTA prevent clotting?

Answer 3

By binding (chelating) calcium required for fibrin clot formation

Question 4

Ideal analysis time of specimens for CBC testing

Answer 4

Within 6 hours of collection if stored at RT
Within 24 hours of collection if stored at 4C

to minimize spurious results

Question 5

Peripheral blood smears should be analyzed within ______ hours of collection to reduce ___ _________ and ________ _______.

Answer 5

Peripheral blood smears should be analyzed within 3 hours of collection to reduce cell deterioriation and morphology artifacts.

Question 6

Most common and currently used hemacytometer

Answer 6

Levy Chamber with Improved Neubauer ruling

Question 7

Size of 1 WBC square on the hemacytometer

Answer 7

1mm^2

Question 8

Size of 1 RBC square in a hemacytometer

Answer 8

0.04 mm^2

Question 9

Depth of the hemacytometer

Answer 9

0.1 mm

Question 10

General total cell count formula

Answer 10

Total cell count = (# of cells counted x dilution factor) / (area in mm^2 x depth)

OR

Total cell count = (# of cells counted x dilution factor x 10) / (area in mm^2)

Question 11

One mm^3 is equivalent to how many microliter (uL)?

Answer 11

1 uL

Question 12

What is the conversion factor of uL to L?

Answer 12

Multiply by 10^6

Question 13

(3) Diluting fluids for WBC count:

Answer 13

1. 1% buffered ammonium oxalate
2. Weak acid solution
   a. 3% acetic acid
   b. 1% hydrochloric acid

Question 14

Purpose of diluting fluid in WBC count

Answer 14

To remove nonnucleated RBCs in the specimen and prevent their interference in the count.

Question 15

Typical dilution for WBC counting

Answer 15

1:20

Question 16

Where are WBCs counted in a hemacytometer?

Answer 16

4 corner squares (total of 4 mm^2)

Question 17

After creating the 1:20 dilution for WBC counting, how many minutes should you wait for the RBCs to lyse?

How long should you perform the count?

Answer 17

10 minutes, within 3 hours of dilution

Question 18

For WBC counting: After charging the hemacytometer, place it in a moist chamber for ____________ to allow the WBCs to settle.

Answer 18

For WBC counting: After charging the hemacytometer, place it in a moist chamber for 10 minutes to allow the WBCs to settle.

Question 19

Under what objective is WBC counting read?

Answer 19

Low Power Objective (10x)

Total of 100x magnification (if with ocular 10x)

Question 20

For WBC counting: The difference between the two counting chambers should be less than how many percent?

Answer 20

10%

Question 21

For WBC counting: When comparing the counts for the two chambers, how do you get the % difference?

Answer 21

% difference = [(V1 - V2) / ( [V1 + V2]/2)] x 100

Question 22

1. What should you do if the percent difference is less than 10%?
2. What should you do if the percent difference is more than 10%?

Answer 22

1. Compute for the WBC count.
2. Repeat the dilution and charging, then recount the WBCs on the hemacytometer.

Question 23

Any nucleatd red blood cells (nRBCs) present in the specimen are not lysed by the diluting fluid. They are counted as WBCs because they are indistinguishable. What is the minimum number of nRBCs per 100 WBCs that must be observed before making a corrected WBC count?

Answer 23

5 nRBCs

Question 24

What is the formula for the corrected WBC count?

Answer 24

Corrected WBC count = (uncorrected wbc count x 100) / (number of nRBCs per 100 WBCs + 100)

Reporting: report as corrected

Question 25

What is the type of WBC differential count routinely performed?

Answer 25

100-cell differential

Question 26

When the WBC count is >40 x 10^9/L, what kind of WBC Differential must be performed?

Answer 26

200-cell differential.

Question 27

When is the 200-cell differential performed?

Answer 27

• WBC count exceeds 40 x 10^9/L
• more than 10% eosinophils
• more than 2% basophils
• more than 11% monocytes
• more lymphocytes than neutrophils (except in children)

Question 28

When is the 300-cell differential performed?

Answer 28

When the WBC count is more than or equal to 100 x 10^9/L

Question 29

When is the 50-cell differential performed?

Answer 29

• WBC count is less than 1.0 x 10^9/L

Question 30

How is the 50-cell differential performed?

Answer 30

• WBC count performed on buffy coat smear
• Count 50 WBCs, then multiply the result by 2 to get a percentage
• Report the results as RELATIVE COUNT

Question 31

Not as accurate or informative as absolute count:

Answer 31

Relative count

Question 32

What is the formula for RELATIVE COUNT

Answer 32

(no of specific WBC TYPE / 100 WBC counted) x 100

Question 33

Reference ranges for relative count

Answer 33

Neutrophil - 51% to 67%
Lymphocyte - 25% to 33%
Monocyte - 2% to 6%
Eosinophil - 1% to 4%
Basophil - 0 to 1%

Question 34

What is Absolute count?

Answer 34

Gives the number of specific WBC type per cubic millimeter of blood
More informative than relative count

Question 35

What is the formula for Absolute count?

Answer 35

Relative count % x WBC count

Question 36

What are the reference values for Absolute count?

Answer 36

Neutrophil - 1600 to 7260/uL
Lymphocyte - 960 to 4400/uL
Monocyte - 180 to 880/uL
Eosinophil - 45 to 440/uL
Basophil - 45 to 110/uL