2. Automated Analyzers and Definitions Flashcards
What is the definition of cytosis/philia
increased cell numbers (ex.
erythrocytosis, neutrophilia)
What is the definition of macro
bigger than normal (ex. macrocytes)
What is the definition of penia
dec cell numbers (ex. lymphopenia)
What is the definition of micro
smaller than normal (ex. microcytes)
What is the definition of normo
normal (ex. normochromic RBC)
What is the definition of poly
increased (ex. polychromic RBC)
What is the definition of hypo
decreased (ex. hypochromic RBC, hypothyroid)
What is the definition of hyper
increased (ex. hyperchromic, hyperthyroid)
What are WBC counts also known as?
Total leukocyte count
What 3 types of blood cell analyzers are there?
impendance analyzers
laser flow cytometry analyzers
quantitative budfy coat analysis sysmtes
How does an impedance analyzer classify cells?
classifies cells based on their size
How is an impedance analyzer work?
electric current passed across 2 electrodes separated by glass tube w/ small opening
electrolyte fluid used as conductor
specific V of cells in electrolyte solution is passed thru opening of glass by vacuum or pos pressure
cells no conduct e current well, so “impedes” flow while passing thru
small changes deterime the cell
What can impedance analyzers differentiate?
size of cell is porportional to the change in current. System is able to differentiate btw cell types like RBCs, WBCs, and platelets
^^ can be inaccurate in cats bc RBC’s and platelets are similar
unreliable in exotics because similar cell sizes
cell size info may be shown in histogram
How does an impedance analyzer count WBC’s, RBC’s and PCV?
WBC: a lytic or lysing agent which lyses platelents and RBCS and are not counted.Fragile WBCs can be lysed to dec total WBC total
RBC: counted without lytic agent and at higher dilution, size can also be determined
RBC analysis provides info on cell volume, PCV and can use cell V to determine mean corpuscular volume
What is the impedance analyzer disadvantages?
variation of cell size produces errors
does not ID morphologic abnormalities - a thorough exam of differential blood film must also be used to eval patients
nucleated RBCs, large platelets and platelet clumping create inaccurate results
machines need daily cleaning bs dust particles can affect results or cause blockages
room temp
How does quantitive buffy coat system classify cells?
uses centrifugation and staining to estimate cellular elements’
the buffy coat layer is expanded within a specialized hematocrit tube and the use of a specialized bead
provides a hematocrit value, estimate of leukocyte concentration, and a platelet concentration
What does quantitive buffy coat system give, what are its limitations?
gives partial differential count of granulocytes, monocytes, and lymphocytes
limitations bc abnormalities may be undetected = blood smear exam is req
type of system only used as screening test bc provides estimates of cell numbers, not actually cell counts
How does laser flow cytometry classify cells?
uses focused laser beams to eval size and density of the cells
How does laser flow cytometry work?
cells scatter light differently depending on shape, V, #, and size of granules and nuclei
cells flow past the laser in a single file through a channel
how light is refracted and picked up on the other side of the tube determines cell type
dyes can be used to help classify
can enumerate monos, lymphos, granulos, mature/immature RBCs, erythrocyte indices, red cell distribution width, and platelet parameters
What are histograms? How are the respresented and what do they determine?
provide a visual representation of # and sizes of cell types
size on the X axis and # on the y
represented by scatter w/ each dot as a cell
determines - average size of cells, distribution of cell size, detect subpopulations, evidence of anomalies
Are histogram diagnostic?
no, just for screening. They tell you that you need to look at a blood film
also used as a quality control measure
What are total leukocyte counts?
a specific V of blood used to count the total number of WBC
results will be reported to the # of WBCx10^9/L
it gives us limited info so essential to know what % of each WBC type of leuko gram is composed of. AKA differential count
How is a total leukocyte count performed?
with leuko=tic system OR by automated analyzers
leuoko-tic system is mantual counting system that uses a blood diluting solution and a hemocytometer
some automated analyzers use the same blood diluting solution and the leuko-tic system
how do we estimate WBC
used as a quality control measure for both manual and automated counts
estimate of t WBC is done w/ differential blood smear
#WBC/high dry field x2 ~ # WBC x 10^9L
Average the # of WBC/field in 10 fields
How do we interpret leukograms
- look at total leukocyte and differential counts
this number is used to calculate the absolute differential counts
total leukocyte count x cell %
ex. neutrophils represent 60% of the WBC’s in the differential cound; total WBC count is 10.0x10^9/L - absolute neutrophil count = 10.0x10^9/L x 60% = 6.0x10^9/L
What do we look at for dec, inc and normal leukocyte counts?
Dec - look @ absolute count for each cell and determine which is dec
Inc - look @ absolute count for each cell and determine which is inc
Normal - look @ absolute count for each cell and determine which is within its normal reference range
What are we interpretation when looking at leukograms
- look at the total leukocyte and differential counts
- look for morphological abnormalities
- look for abnormal cell types (atypical cells)
- Immature cell stages
What do automated machines count in regards to total leukocyte counts?
count all nucleated cells, may include nucleated RBC’s
will cause total leuko count to be artificially high
mathematical adjustments will be req when nucleated RBC’s are seen on the differential smear
What do you look for when looking for abnormal cells of a leukogra?
these cells didn’t divide as often during development, or cytoplasm and nucleus develop along diff courses
-usually only classified as granulocyte or agranulocyte and are recorded as atypical cells on the differential blood film report sheet
-1-2% is normal and are not recoded on report sheet
in doubt, ask for 2nd opinon
What are the 3 categories of chem analyzers?
1 photometry is most common
electrochemical
light-scatter techniques
Explain how photometry work
machines used is a spectrophotometer which prods light of various wavelengths via filters, prisms or diffraction gratings
Spectrophotometers are designed to measure the amount of light transmitted thru a solution
Has basic components such as a light source, prism, wavelength selector, photodetector and a read out device
What are the most common techniques used by photometry machines?
Absorbance - how much light did NOT reach the detector ( uses wet/rotor technology)
Reflectance - how much light was reflected off a test substance (used by most in-house analyzers, uses a dry/slide chem system
What is Beer’s law?
a direct linear relationship btw the conc of an analyte and the light absorption when monochromatic light is passed thru the sample
The transmission of the monochromatic light thru a sample and the conc of an analyte in the sample have an inverse exponential relationship
the degree of color change is proportional to the solution’s conc
How do we explain beer’s law in simple terms?
When we know how much light is prod + how much of that light passed thru the solution to the detector, we can calculate the amount of light that was absorbed by the patient sample
Analyte - what we are measuring. Ex. K
High conc of analyte: more light absorbed as passes thru the solution = less light will reach detector
Low con of analyte: less light is absorbed as it passes thru the solution = more light will reach the detector
The higher the conc of analyte the greater the color change of the detector
What are the 2 types of absorban array methods?
- end point
- kinetic
What is the endpoint method of an absorbance assay method?
measures the conc of pre-existing substances in the serum or plasma
involves a chem reaction that reaches a /stable end point/ and measures the color change
an int standard curve is created when the instrument is calibrated - must be recalibrated w/ each new reagent. A standard is used for calibration
Explain how the kinetic method of absorbance assay method works
generally used to measure enzyme assays or when enzyme based reagents are used
reaction results are measured at a specific time after the initiation of the reaction
does NOT reach a stable end point
What do we need to keep in mind with enzymes in regards to analyzers?
Enzyme activity is greatly inhibited by low temperatures and accerlated by high temps
Most assays performed btw 30-37C (for every 10C inc above optimal temp, enzyme activity doubles. Monitor incubators and water baths closely)
enzymes are proteins! they are denatured by temp, pH extremes, organic solvents, heavy metals or physically damage. HANDLE CAREFULLY
Explain how electrochemical methods of analyzer works
AKA ion-selective electrode (ISE) technology
some use this + photometric methods
Common to measure electrolytes
Diff in electrical potential btw the electrodes is proportional to the conc of the ion in the sample
Which method is also referred to as potentiometers?
Potentiometer contains reference electrodes - reference electrodes interact w/ only ONE type of ion and contain a known conc of that ion
The patient sample interacts w/ a second ion specific electrode which is located within biosensor reagent strip or cartridge
there is a voltage diff btw the electrodes which is used to calculate the conc of the ion in the sample
How does light scatter techniques work?
used to measure the conc of larger molecules in fluids like immunoglobulins, AG-AB complexes, drugs, etc
detects the reduction of the intensity of a light as it passes from the light source, thru a solution
What are the features and benefits of automated analyzers
Automated analyzers use liquid reagents, dry reagents or slides that contain dry reagents
almost all systems can now be integrated so that results are inserted directly into the patients e-file (eliminates missed charges and accessible thruout hospital
What are dry systems?
these incluse systems that use reagent impregnated slides, pads or cartridges (catalyst Dx and VetTest)
Most used reflectance photometry
There is little to no handling or storage concerns for reagents
tend to be a little more expensive to run
Sample rejection is common particularly w/ lipemic, hemolyzed or large animals amples
can perform individual or single assay tests
slides do allow for loading of a large # of slides at once reducing time needed to run a complete profile
How do lipid systems work?
include systems that use lyophilizes reagent or already prepared liquid reagent
most common is lyophilized rotor technology (vet scan, rotor is made up of individual cuvettes that diluted sample is added to) cannot run individual tests
What are the pros and cons of liquid systems
tend to be quite accurate
require more handling and storage space
unitized systems require less handling but are more expensive
there are also systems that use bulk reagents (these systems can run individual tests, reagent solutions may or may not need to be diluted, some have extensive maintenance requirements)
What is a dedicated use analyzer
most utilize electrochemical methods
used to test a specific substance
are used when only once substance is being tested
blood glucose monitors (alpha trak 2)
