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Hematology > Units 10&11 - Instrumentation/Automation > Flashcards

Units 10&11 - Instrumentation/Automation Flashcards

(65 cards)

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1
Q

The Coulter Principle

A

Counting particles/cells by electrical impedence

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2
Q

Principle of Coulter electrical impedence counters

A
  • Particles in a conductive fluid with current running through
  • Particles are bad conductors
  • Particles are sent in single file, they interrupt the current and that increases resistance creating a voltage pulse
  • Amount of voltage pulses = cell count
  • Amplitude (height) of each pulse = cell size
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3
Q

Early Coulter counters

A

One type of cell counted at a time
(ex. RBC at 60-120 fL)
Dilutions done manually, either for RBC WBC or PLT

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4
Q

Later Coulter Multiparameter Instruments

A

Counted different cells in separate counting chambers
Machine made dilutions and directed cells to appropriate channels

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5
Q

Coulter Model S in 1960s

A

Later multi parameter Coulter instrument

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6
Q

Modern Analyzers using Coulter principles

A

Lasers - fwd & side scatter
High freq. probe for conductivity
Retic count added
Slide makers added
Stainers added

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7
Q

Types of specimen for heme analyzers

A

Whole blood - WBC, RBC, PLT
Body fluids

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8
Q

How do cell counts differ in body fluids from whole blood

A

Body fluids have LOW cell counts
Proportion of WBC and RBC often inverted

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9
Q

RBC cell counts performed in what kind of solution

A

Isotonic solution (saline diluent)
Dilution very high so only one RBC read at a time

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10
Q

What must be done if high amount of WBC due to leukemia when automated RBC count?

A

Mathematical correction

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11
Q

WBC cell counts performed how

A

Diluted in fluid that lyses RBC
Similar to hemacytometer method
Same channel used to measure hgb; WBC diluent contains cyanide reagent for cyanmethemoglobin method

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12
Q

PLT cell counts performed how

A

In the same channel as RBCs
Instrument separates populations as to size

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13
Q

1fL = xliter

A

10^-15 L

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14
Q

1fL = xmililiter

A

10^-12 mL

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15
Q

1fL = xmicroliter

A

10^-9 mcL

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16
Q

x axis and y axis of histogram for cell counts

A

X axis: size
Y axis: frequency/count

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17
Q

Usual units for cell volume

A

femtoliter

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18
Q

Uses of histograms

A

RBC:
MCV, RDW, Visible interferences like clumped PLTs

WBC:
3 part diff on low end models

PLT:
MPV

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19
Q

Coincidence

A

Multiple cells passing through aperture at same time

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20
Q

How do coincidences skew values

A

False increase pulse height
False decrease cell count

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21
Q

How to fix coincidences

A

Decrease aperture size
Hydrodynamic focusing
Instrument software that edits out bad pulses
Correction tables
Dilute sample

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22
Q

Hydrodynamic focusing

A

Forcing cells into single file

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23
Q

Coincidences more common in specimen with..

A

High cell counts

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24
Q

Thresholds

A

Setting upper and lower size limit of each cell type

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25
How thresholds are set for RBCs
Separate RBCs and PLT
26
How thresholds are set for WBCs
Granulocytes - Largest Monos Lymphs - Smallest
27
Action levels
Ranges for which counts are acceptable
28
Below action level
SLide review Manual count
29
Above action level
Dilute Repeat Multiply by DF
30
Critical Values
Instrument result acceptable but has serious consequences for patient Phone doctor immediately
31
Instrument flags/Prompts
Abnormalities detected MLS must investigate
32
If two or more of the triplicate counts are not in agreement range -->
No result reported
33
3 Part Differential
Histogram of: Lymphs Monos Granulos
34
Lymphocyte size after diluent applied
35-90fL
35
Monos size after diluent applied
90-160 fL
36
Granulos size after diluent applied
160-450 fL
37
5 Part Differential
Scatter plot - Coulter VCS Volume Conductivity Scatter Diluent keeps them in near native state
38
Which differential keeps the cell sizes in near native state
5 part diff
39
Volume (VCS)
Direct current Essentially impedence Cell size in fL
40
Conductivity (VCS)
High frequency current Measures opacity based on N/C ratio, nuclear density, granularity
41
Scatter (VCS)
Laser light scatter Internal structure Granularity Surface Characteristics
42
Components of multi parameter Coulter like instrument
Specimen loading bay and rocker Dilutor, tubing, channels to route cells Counting chambers for WBC RBC Hgb Power supply
43
Coulter Reticulocyte Method
In separate channels, RBCs mixed with new methylene blue and diluent Retics counted and reported as absolute amount Comparison of retic maturity on scattergram and PBS
44
Coulter Reticulocyte Diluent
Contains acid to remove hgb, leaving mRNA to stain Hypotonic to convert all RBC to spherocytes - removes error based on shape
45
How are measured CBC values run
Triplicates
46
What are measured CBC values
MCV WBC RBC Hgb PLT count
47
What are calculated CBC values
MCHC MCH Hct RDW MPV 3 or 5 part diff Percent/abs counts for each WBC type
48
Which hct is higher? calculated or spun?
Spun because of trapped plasma between RBCs
49
Errors with Coulter-like instruments
Carryover False increase in hgb increased MCV decreased RBC
50
How is hgb measured in CBC
Cyanmethemoglobin Same as manual
51
When is carryover a problem?
If next specimen has low counts
52
Why would false increase in hgb occur
Elevated WBC Elevated lipids (false inc in absorbance)
53
Why would increase in MCV and decrease RBC happen
Cold agglutinins Rouleaux (clumping)
54
What would you do to a specimen that has an issue with its plasma?
Replace plasma with saline
55
What occurs in specimen with too much EDTA
RBC shrinkage Hct false decrees MCV and MCHC decreased
56
When would a specimen have too much EDTA?
Underselling a tube
57
MCHC calculated formula
(Hgb) * 100 / Hct
58
MCH calculated formula
Hgb*10 / RBC
59
Hct Calculated formula
MCV * RBC / 10
60
RDW formula
CV of RBC size distribution
61
Sysmex hematology analyzers scatterplot axes
X -Side Scatter Y -Side Fluorescence
62
Techniques used by Sysmex
Absorption spectrometry - SLS hgb method Hydrodynamic focusing = single file (no physical aperture) Counts cells by direct current (impedance) Fluorescent flow cytometry (stains DNA) Radio frequency
63
Absorption spectrometry - SLS hgb method
Separate channel on instrument for hgb Diluent lysis RBC SLS (sodium laurel sulfate) converts Fe++ to Fe+++ for methemoglobin Methgb combines with SLS --> chromatin absorbs at 555 nm Run is fast with NO CYANIDE
64
Hydrodynamic focusing and impedence
Same as Coulter only no physical aperture
65

Hematology (12 decks)

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