Chapter 11: Manual, Semiautomated, and POCT Flashcards
Most common anticoagulant in routine hematology testing
Ethylenediaminetetraacetic acid (EDTA)
Form of EDTA usually used in routine Hematology
K2EDTA
How does EDTA prevent clotting?
By binding (chelating) calcium required for fibrin clot formation
Ideal analysis time of specimens for CBC testing
Within 6 hours of collection if stored at RT
Within 24 hours of collection if stored at 4C
to minimize spurious results
Peripheral blood smears should be analyzed within ______ hours of collection to reduce ___ _________ and ________ _______.
Peripheral blood smears should be analyzed within 3 hours of collection to reduce cell deterioriation and morphology artifacts.
Most common and currently used hemacytometer
Levy Chamber with Improved Neubauer ruling
Size of 1 WBC square on the hemacytometer
1mm^2
Size of 1 RBC square in a hemacytometer
0.04 mm^2
Depth of the hemacytometer
0.1 mm
General total cell count formula
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)
One mm^3 is equivalent to how many microliter (uL)?
1 uL
What is the conversion factor of uL to L?
Multiply by 10^6
(3) Diluting fluids for WBC count:
- 1% buffered ammonium oxalate
- Weak acid solution
a. 3% acetic acid
b. 1% hydrochloric acid
Purpose of diluting fluid in WBC count
To remove nonnucleated RBCs in the specimen and prevent their interference in the count.
Typical dilution for WBC counting
1:20
Where are WBCs counted in a hemacytometer?
4 corner squares (total of 4 mm^2)
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?
10 minutes, within 3 hours of dilution
For WBC counting: After charging the hemacytometer, place it in a moist chamber for ____________ to allow the WBCs to settle.
For WBC counting: After charging the hemacytometer, place it in a moist chamber for 10 minutes to allow the WBCs to settle.
Under what objective is WBC counting read?
Low Power Objective (10x)
Total of 100x magnification (if with ocular 10x)
For WBC counting: The difference between the two counting chambers should be less than how many percent?
10%
For WBC counting: When comparing the counts for the two chambers, how do you get the % difference?
% difference = [(V1 - V2) / ( [V1 + V2]/2)] x 100
- What should you do if the percent difference is less than 10%?
- What should you do if the percent difference is more than 10%?
- Compute for the WBC count.
- Repeat the dilution and charging, then recount the WBCs on the hemacytometer.
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?
5 nRBCs
What is the formula for the corrected WBC count?
Corrected WBC count = (uncorrected wbc count x 100) / (number of nRBCs per 100 WBCs + 100)
Reporting: report as corrected
What is the type of WBC differential count routinely performed?
100-cell differential
When the WBC count is >40 x 10^9/L, what kind of WBC Differential must be performed?
200-cell differential.
When is the 200-cell differential performed?
- 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)
When is the 300-cell differential performed?
When the WBC count is more than or equal to 100 x 10^9/L
When is the 50-cell differential performed?
- WBC count is less than 1.0 x 10^9/L
How is the 50-cell differential performed?
- 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
Not as accurate or informative as absolute count:
Relative count
What is the formula for RELATIVE COUNT
(no of specific WBC TYPE / 100 WBC counted) x 100
Reference ranges for relative count
Neutrophil - 51% to 67%
Lymphocyte - 25% to 33%
Monocyte - 2% to 6%
Eosinophil - 1% to 4%
Basophil - 0 to 1%
What is Absolute count?
Gives the number of specific WBC type per cubic millimeter of blood
More informative than relative count
What is the formula for Absolute count?
Relative count % x WBC count
What are the reference values for Absolute count?
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
