Blood Cell Analyzers

Primary mode of operation

• automatic

• multiple samples are mixed, aspirated and analyzed automatically from the primary tubes (closed system)

Secondary mode of operation

• manual

• samples mixed manually and caps are removed

• patient information and tests entered manually

• each sample is run individually via the secondary aspiration mode

Maintenance of blood analyzers is essential for ensuring what?

• accurate and reliable results

• extending equipment lifespan

• preventing failures

• maintaining compliance with regulatory standards

How does electrical impedance work?

cells moving into the aperture tube creates measurable pulses that correlate with number and size of cells - size of pulse directly proportional to size of cell

How does a volume distribution histogram work?

the number of pulses generated os directly proportional to the number of cell being counted and the height of the pulse is directly proportional to the size of the cell passing through the aperture

What histograms are generated using volume distribution histograms?

WBC, RBC & PLT

What causes lower cell counts and falsely elevated cell volumes?

• Protein buildup

• smaller aperature

• slower cell flow

• increased relative electrical resistance

What is coincidence correction?

corrects for more than one cell passing through at the same time

What is the sweep flow line?

prevent recirculating of cells back into the sensing zone

What is isovolumetric sphering?

Biconcave RBCs are sphered to avoid misaligning as they pass through an aperture

What is flow cytometry?

sheath fluid or laminar flow is used to align cells in the center of the aperture = more reliable and accurate counts

What can cause pulse height irregularities with flow cytometry?

cells close to the outer areas

The use of flow cytometer for cell counting can cut down on what?

• protein buildup

• eliminates sensing zone recirculation issues

• reduces pulse interferences

What is radiofrequency conductivity?

DC (low frequency current) and RF (high current frequency) flows across an aperture between two electrodes and the DC current measures cell volume as cells pass through. As the cells pass through the RF current penetrates the cell membrane and measures the internal complexity

The amplitude of the pulse generated with radiofrequency conductivity is dependant on what?

the cell density and internal complexity

What reduces radiofrequency conductivity?

• high nuclear-cytoplasmic ratio

• nuclear density

• cytoplasmic granulation

Total volume of the cell is proportional to the?

DC impedance

Internal complexity is proportional to?

RF signal

The number of dots on a scatter plot is proportional to what?

the # of cells

Optical light scatter

uses a flow tube to stream fluid through a quartz flow cell and passes through a light source - tungsten-halogen lamp or helium-neon laser

Optical light scatter: the number of pulses generated is directly proportional to what?

the number of cells passing through the sensing zone in a specific period

Absorption

light absorbed by components within the cell (does not penetrate the cell)

Diffraction

bending around corners or surfaces of cells

Refraction

bending due to change in speed

Reflection

backward scatter of rays due to an obstruction

Forward angle light scatter

0 degrees - correlates with cell volume, mainly due o the diffraction of light

Side light scatter

90 degrees - measures the large structures inside the cell and correlates with internal cellular complexity

Cytochemical/Fluorescent staining

used in combination with optical light scatter can identify and count blood cells

How does Cytochemical/Fluorescent staining work?

absorbs laser light at one wavelength and then emits fluorescent light at a higher wavelength that is specific to a particular fluorescent dye

What is an example of higher intensity concentration?

the more immature the reticulocyte or platelets are the greater the concentration of RNA

What method of Hemoglobin measurement does the Beckman Coulter use?

Cyanmethemoglobin

What method of Hemoglobin measurement does the Sysmex use?

Sodium Lauryl Sulfate

Beckman Coulter hemoglobin measurement

RBCs are lysed in the WBC bath freeing HGB. The HGB is converted to a stable pigment and measured at 525nm. the more pigment absorbed, the higher the HGB concentration in the sample

Sysmex Hemoglobin measurement

SLS lyses RBCs and WBCs, this alters the globin chains and exposes the heme group. The heme group is then oxidized allowing the SLS reagent to form a stable colored complex with the heme portion. Analyzed via photometric method where the amount of light absorbed is proportional to the HGB concentration.

Why is Sysmex (SLS) measurement better?

it eliminates the used of cyanide and is further minimizes interferences with extremely high WBC counts, lipemia, and abnormal proteins