Automated Testing Flashcards
Principle of electronic impedance in cell counting. What is it based on?
- cells suspended in conductive liquid (Isotonic diluent) that acts as electrical insulators
- flow of current is established between two submerged electrodes
- cells pass through an aperture by gentle vacuum/hydrodynamic focusing* = pulses and resistance to electrical flow can be counted and sized as a particle
*NOTE: Beckman vs Sysmex
Purpose of diluent in cell counting baths
“Number of voltage pulses” represents which hematologic parameter ?
Cell count
“Height of voltage pulses” represents which hematologic parameter ?
Cell volume
Define “co-incidence” in hematology
- 2 or more cells pass the aperture at the same time = 1 pulse counted as 1 cell
- cell count is falsely decreased and pulse height is falsely increased
How are histograms created ?
What is “aperture voting ?”
- Values counted in triplicate must match
- If 2/3 match = partial vote out
- If 2 or all 3 values do not match = total vote out
How is Hb value determined on Beckman Coulter ?
- lysing agent added to WBC dilution = lyses RBCs + release Hgb
- AFTER WBC COUNT, sample is taken to the SPECTROPHOTEMETER where Hgb is measured at 525nm
How is Flow Cytometry used to study cells ?
Forward light scatter: cell size
Side scatter: cell complexity/ granularity
VCS in Beckman Coulter analyzers
- differentiate WBCs
Volume:
Conductive:
Light Scatter:
Which WBCs are included in the 6-part differential on the Sysmex ?
- neutrophils
- lymphocytes
- monocytes
- eosinophils
- basophils
- myeloids
How do Sysmex analyzers differentiate WBCs ?
- fluorescent flow cytometry differentiates WBCs
- fluorescence = RNA/DNA content
- forward scatter = cell size
- side scatter = granularity/cell complexity
- polymethine dye is used to stain WBCs
- 6-part differential includes: neutrophils, lymphocytes, monocytes, eosinophils, basophils, and immature granulocytes /myeloids
Significance of increased retic count
Anemia due to red blood cells being destroyed earlier than normal (hemolytic anemia)
3 general causes of increased retic count
- Hemolytic anemia
- Blood loss
3.
How do Beckman Coulter determine retic count ? What parameters are used and how are they measured ?
- sample in stain chamber = NEW METHYLENE BLUE precipitates DNA in immature RBCs (increases granularity)
- VCS technology differentiates other cells from retics (decreased size and granularity)
How do Sysmex analyzers determine retic count ? What parameters are used and how are they measured ?
When would a manual retic count be indicated instead of an automated count ?
What stain is used for manual retic counts ? What does this stain do to retics ?
New methylene blue; causes clumping and staining of residual nucleic acid present in immature cells.
Minimum requirement for a stained red cell to be a retic
Manual staining procedure for retics (dilution, incubation time, etc.)
Manual counting procedure for retics (relative and absolute counts)
What are the allowable ranges (technical accuracy limits) when comparing retic counts on two slides ?
0 - 2%=
2.1 - 5%=
>5% =
Ref: relative retic count (>1 week old)
Ref: absolute retic count (>6 months old)
MCV (fL)
HCT/RBC x 1000
MCHC (g/L)
HGB/ HCT
MCH
HGB/ RBC
WBC estimate when 35 WBC /3 lpf and WBC field factor = 4
2.9 x10^9/L
PLT estimate when 260 PLT /10 hpf and PLT field factor = 14
364 x10^9/L
What is measured using electrical impedance in the 2-20fL range ?
PLT count
What is calculated directly from the RBC histogram ?
RDW
What is determined by the cumulative pulse height of RBC on Sysmex analyzers ?
HCT
What is measured only by electrical impedence in either Sysmex or Beckman-Coulter analyzers ?
RBC count
What is calculated using hemoglobin and RBC count on Beckman-Coulter analyzers ?
MCH
What is calculated using hematocrit and RBC count on Sysmex analyzers ?
MCV
What is measured by forward light scatter and side fluorescent light detection on Sysmex analyzers ?
WBC count
Crit: Hgb
Adult: <70 g/L
<8 days: <70 g/L
All: >239 g/L
Crit: WBC count
<0.6 x10^9/L
>99.9 x10^9/L
Crit: PLT count
Inpt: <10 x10^9/L
Outpt: <20 x10^9/L
Which of the following is true regarding automated reticulocyte counts?
a.
Reticulocytes will have decreased electrical impedance compared to mature RBC
b.
Reticulocytes will have decreased forward scatter compared to mature RBC
c.
Reticulocyte RNA content determines optical light scatter
d.
Reticulocyte fluorescence increases with maturity on Sysmex analyzers
c.
Reticulocyte RNA content determines optical light scatter
Which of the following statements about RBC counts on a Beckman analyzer is(are) true? Select all that apply:
a.
RBCs are counted if they are >35fL
b.
RBCs are counted in the same bath as PLT
c.
A lysing agent is added to dilute the sample prior to counting
d.
RBCs are counted as they impede the flow of a current
a.
RBCs are counted if they are >35fL
b.
RBCs are counted in the same bath as PLT
d.
RBCs are counted as they impede the flow of a current
Which of the following parameters will be affected by lipemia in the sample? Select all that apply:
a.
RBC count
b.
MCH
c.
MCHC
d.
Hemoglobin
b.
MCH
c.
MCHC
d.
Hemoglobin
NOTE: RBC count is determined by electrical impedance, not spectrophotometry
Which of the following interferences are eliminated by performing a fluorescent platelet count (PLT-F) on Sysmex analyzers? Select all that apply:
a.
PLT clumps
b.
Schistocytes
c.
Very small RBCs
d.
Giant PLT
b.
Schistocytes
c.
Very small RBCs
d.
Giant PLT
How is the WBC count determined on Beckman Coulter analyzers?
Electrical Impedance
A patient’s WBC count on a Beckman analyzer is 480.4 x 109/L. Which of the following parameters will be unaffected?
a.
MCHC
b.
PLT count
c.
RBC count
d.
Hemoglobin
b.
PLT count
How is the platelet count determined on Beckman analyzers?
Electrical impedance
How can precision checks be performed on hematology analyzers?
a.
A normal patient is analyzed 6 times and the SD is calculated
b.
A normal patient is analyzed 6 times and the CV is calculated
c.
A commercial whole blood control is analyzed 6 times and the SD is calculated
d.
A commercial whole blood control is analyzed 6 times and the CV is calculated
b.
A normal patient is analyzed 6 times and the CV is calculated
Formula for corrected WBC
(absolute WBC x 100) / (nRBC + 100)
T or F: The Giemsa stain is a nuclear stain and demonstrates inclusions well
TRUE; the Giemsa stain is a nuclear stain and demonstrates inclusions well
Select reportable:
- 3-6 shistocytes /100 RBC
- PLT est = 85 x 109/L
- 1-2 hypochromic cells/100 RBC
- 1-2 tear cells/100 RBC
- 1 Howell-Jolly
3-5% shisctocytes
A patient has been admitted to the ED after a car accident. They were bleeding profusely and transfusion testing is currently underway to cross-match 2 units of packed cells.
CBC results showed:
Hgb = 69 g/L
PLT = 89 x 10^9/L
PBS:
3-6 shistocytes /100 RBC
PLT est = 85 x 109/L
1-2 hypochromic cells/100 RBC
1-2 tear cells/100 RBC
1 Howell-Jolly
Is there any other follow-up required for this patient?
- critical Hgb called to the ward
- pathologist notified of schisto + low PLT and smear left to be reviewed
