Automation hematology Flashcards by pattie o.

BASIC COMPONENTS OF MOST HEMA ANALYZERS

Hydraulics, Pneumatics, Electrical systems

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Aspirating unit, dispensers, dilutors, mixing chambers, aperture baths, flow cells, hemoglobinometer

Hydraulics in HEMA analyzers

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Vacuum and pressure systems for operating valves and moving samples

Pneumatics in HEMA analyzers

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Electrical systems in HEMA analyzers

Electronic analyzers, computing circuitry for data processing

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ELECTRICAL IMPEDANCE principle

Cell counting

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Origin of Electrical Impedance

Developed by Coulter in the 1950s

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Most common methodology for cell counting

Electrical Impedance (Coulter Principle)

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Radiofrequency (RF) in electrical impedance

Modification of DC impedance, measures conductivity, AKA alternating current

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Cell counting in electrical impedance is based on the detection and measurement of changes in electrical impedance (resistance) produced by a particle as it passes through

Aperture

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Impedance change during cell passage

Caused by non-conductive particles (cells) in an electrically conductive diluent

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Pulse generation in electrical impedance

Proportional to the number of cells passing through the aperture

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Pulse amplitude in electrical impedance

Indicates the cell’s volume

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Radiofrequency (RF) in electrical impedance

Measures conductivity and changes in RF signal reflect cell interior density

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Two-dimensional distribution cytogram

Plots RF conductivity and DC impedance of cells

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Displays clusters of cells, representing concentration of a specific cell type in electrical impedance

Scatterplot

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Also known as Electronic Resistance or Coulter Principle

Electrical impedance

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Instrumental Error: Most common problem in cell counting, produces POSITIVE (+) ERROR

Aperture plugs

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Instrumental Error: Caused by too vigorous mixing, produces POSITIVE (+) ERROR

Bubbles in the sample

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Instrumental Error: Produces POSITIVE (+) ERROR

Extraneous electrical pulses

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Instrumental Error: Produces NEGATIVE (-) ERROR

Excessive lysing of RBCs

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Instrumental Error: Incorrect aperture current/threshold settings, may cause POSITIVE (+) or NEGATIVE (-) ERROR

Improper settings of aperture current/threshold

Specimen Error: May be counted as RBCs or WBCs

Giant platelets

Specimen Error: May be counted as platelets or RBCs, seen in leukemia therapy

Fragments of WBC cytoplasm

Specimen Error: May cause falsely elevated (↑) WBC counts

Some abnormal RBCs (e.g., sickle cells, hypochromic cells, target cells)

RBC histogram: RBC count range in fL

36 fL to 360 fL

RBC histogram curve shift right

RBCs larger than normal

RBC histogram curve shift left

RBCs smaller than normal

Bimodal RBC histogram curve indicates

Two populations of RBCs (e.g., post-transfusion, cold agglutinin disease, hemolytic anemia with schistocytes, mixed anemias)

RBC histogram: Minimum cell size measurable

24 fL

Cells between 24 to 36 fL in RBC histogram

Rejected as RBCs, not included in RBC count

Leukocytes in diluted RBC fluid

Statistically insignificant, unless leukocyte count is elevated

Instrument calibration for leukocytes in RBC histogram

Compensates for leukocytes' presence

Effect of significantly elevated leukocyte count

Affects the erythrocyte histogram

Blood cell histograms y-axis

Approximate number of cells

Blood cell histograms x-axis

Cell size

Provide size distribution of the different cell populations

Blood cell histogram

Provide a count and plot of cells larger than 45 fL in aperture bath

WBC histograms

Normal first peak (45-90 fL) in WBC histogram

Small mononuclear cells (e.g., lymphocytes)

Normal second peak (90-160 fL) in WBC histogram

Minor population of large mononuclear cells (e.g., monocytes); may indicate abnormal cells in leukemia

Normal third peak (160-450 fL) in WBC histogram

Normal mature granulocytes

**Region code (R) flags in WBC histogram**

**Signal irregularities** in **WBC distribution**, appear next to error differential parameters

**R1 region** warning in WBC histogram

**Increased interference left of lymphocyte peak** (approx. 35 fL); caused by sickled RBCs, nucleated RBCs, or giant/clumped platelets

**R2 region** warning in WBC histogram

**Excessive overlap of cell populations at lymphocyte/mononuclear boundary** (approx. 90 fL); caused by atypical lymphocytes, blasts, or plasma cells

R3 region warning in WBC histogram

Excessive overlap at mononuclear/granulocyte boundary (approx. 160 fL); **caused by immature granulocytes** (bands, metamyelocytes)

R4 region warning in WBC histogram

**Extension of cell distribution past the upper end of the WBC threshold** (approx. 450 fL); caused by very high granulocyte population

**RM error** code in WBC histogram

**Indicates multiple region overlap**

H flag in histograms

Parameter value is higher than the set normal limit

L flag in histograms

Parameter value is lower than the set normal limit

Platelet histograms derived from electrical impedance method

Obtained from volume sizes of **2 to 20 fL**

Platelet counting in platelet histograms

Occurs in the RBC aperture