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HEM Automated Testing Flashcards

1
Q

Principle of electronic impedance in cell counting. What is it based on?

A
  • 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

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2
Q

“Number of voltage pulses” represents which hematologic parameter ?

A

Cell count

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3
Q

“Height of voltage pulses” represents which hematologic parameter ?

A

Cell volume

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4
Q

Define “co-incidence” in hematology

A
  • 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
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5
Q

What is “aperture voting ?”

A
  • 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
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6
Q

Describe RBC histograms

A

x- axis: cell size (fL)
y-axis: cell count

  • begins at baseline
  • one population with a gaussian distribution
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7
Q

How is Hb value determined on Beckman Coulter ?

A
  • 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
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8
Q

How is Flow Cytometry used to study cells ?

A

Forward light scatter: cell size
Side scatter: cell complexity/ granularity

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9
Q

VCS in Beckman Coulter analyzers

A
  • differentiates nRBCs from WBCs based on

(V)olume: cell size
(C)onductivity: nuclear, granular, and chemical composition of cell interior
Light (S)catter: flow cytometry correlates forward and side scatter

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10
Q

Which WBCs are included in the 6-part differential on the Sysmex ?

A
  1. neutrophils
  2. lymphocytes
  3. monocytes
  4. eosinophils
  5. basophils
  6. myeloids
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11
Q

How do Sysmex analyzers differentiate WBCs ?

A
  • 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
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12
Q

Significance of increased retic count

A

Anemia due to red blood cells being destroyed earlier than normal (hemolytic anemia)

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13
Q

How do Beckman Coulter determine retic count ? What parameters are used and how are they measured ?

A
  • 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)
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14
Q

How do Sysmex analyzers determine retic count ? What parameters are used and how are they measured ?

A
  • RET chamber = lysis reagent perforates RBCs, WBC and PLTs
  • FLUORESCENT markers label nucleic acids in cell
  • Flow cytometry (SS and FS) differentiates RBC from retics (increased size and decreased granularity)
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15
Q

What stain is used for manual retic counts ? What does this stain do to retics ?

A

New methylene blue; causes clumping and staining of residual nucleic acid present in immature cells.

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16
Q

MCV (fL)

A

HCT/RBC x 1000

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17
Q

WIP When would a manual retic count be indicated instead of an automated count ?

A
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18
Q

MCHC (g/L)

A

HGB/ HCT

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19
Q

MCH

A

HGB/ RBC

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20
Q

WBC estimate when 35 WBC /3 lpf and WBC field factor = 4

A

2.9 x10^9/L

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21
Q

Formula: WBC estimate (x10^9/L)

A

total WBC / 10 lpf / 4

NOTE: take average of (10) fields at low power, divide by 4 (field factor)

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22
Q

PLT estimate when 260 PLT /10 hpf and PLT field factor = 14

A

364 x10^9/L

NOTE: take average of (10) fields at hpf, multiply by 14 (field factor)

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23
Q

What is measured using electrical impedance in the 2-20fL range ?

24
Q

What is calculated directly from the RBC histogram ?

25
Which indices is determined by the cumulative pulse height of RBC on Sysmex analyzers ?
HCT
26
What is measured only by electrical impedence in either Sysmex or Beckman-Coulter analyzers ?
RBC count
27
What is calculated using hemoglobin and RBC count on Beckman-Coulter analyzers ?
MCH
28
What is calculated using hematocrit and RBC count on Sysmex analyzers ?
MCV
29
What is measured by forward light scatter and side fluorescent light detection on Sysmex analyzers ?
WBC count
30
Crit: Hgb
<70 g/L >239 g/L
31
Crit: WBC count
<0.6 x10^9/L >99.9 x10^9/L
32
Crit: PLT count
Inpt: <10 x10^9/L Outpt: <20 x10^9/L
33
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
34
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
35
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
36
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
37
How is the WBC count determined on Beckman Coulter analyzers?
Electrical Impedance
38
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 NOTE: high WBC count makes sample cloudy = affects Hgb and MCHC - also interferes in RBC count
39
How is the platelet count determined on Beckman analyzers?
Electrical impedance
40
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
41
Formula: corrected WBC
(absolute WBC x 100) / (nRBC + 100)
42
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
43
Select all that are reportable: a). 3-6 schistocytes /100 RBC b). PLT est = 85 x 109/L c). 1-2 hypochromic cells/100 RBC d). 1-2 tear cells/100 RBC e). 1 Howell-Jolly
3-5% schisctocytes
44
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
45
Cause: Falsely decreased WBC
- WBC fragmentation - WBC clumps - very small lymphs
46
Cause: Falsely increased RBC
- very high WBC count - giant PLTs
47
Cause: Falsely decreased RBC
- cold agglutinins = RBC clump - microcytes - schistocytes - in vitro Hemolysis
48
Cause: Falsely increased PLT
- very small RBCs or WBCs - schistocytes - microorganisms - WBC fragments
49
Cause: Falsely decreased PLT
- PLT clumps - old specimen - giant PLTs - PLT satellitism
50
Cause: Falsely increased HGB
- HIL - very high WBC count = turbid
51
Cause: Falsely decreased HGB
- cells that resist lysis
52
Cause: Falsely increased HCT
- very high WBC - giant PLT
53
Cause: Falsely decreased HCT
- cold agglutinins - **microcytes** - **schistocytes** - in vitro Hemolysis - excess EDTA
54
Cause: Falsely increased MCV
- hyperglycemia and hypernatremia - cold agglutinins - old specimen
55
Cause: Falsely decreased MCV
excess EDTA
56
Cause: Falsely increased MCHC
- HIL - cold agglutinins - very high WBC

CSMLS (46 decks)

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