Unit 3.6 PRINCIPLES OF AUTOMATION IN HEMATOLOGY Flashcards
refers to the use of laboratory instruments and processing equipment to perform clinical laboratory assays with only minimal involvement of the medical technologist
Automation
2 Classic automated methods for counting cells
Coulter Counter
Electronic Impedance/Resistance
Technicon Autoanalyzer; Ortho Diagnostic; Fisher Autocytometer
Optical Detection/Light Scattering
The Basic Components Common to Most Hematology Analyzers
includes the aspirating unit, dispensers, dilutors, mixing chambers, aperture baths, and/or flow cells, and hemoglobinometer
Hydraulics
Vacuum and pressures for operating values and moving the sample through the system
Pneumatics
Electronic analyzers and computing circuitry for processing data
Electrical systems
Blood is diluted in an isotonic solution and drawn through an aperture.
ELECTRIC IMPEDANCE
Since cells are nonconductive, the passage of cell through the aperture increases the resistance (impedance) of the electrical path between 2 electrodes that are located on each side of the aperture.
ELECTRIC IMPEDANCE
Changes in electrical resistance are counted as
voltage pulses.
Number of Voltage pulses is directly proportional to the
number of cells/cell cou nt.
Amplitude/height/size of the pulse is directly proportional to the
volume of the cell
a diluted blood specimen passes through a steady stream through which a beam of LASER light is focused.
LIGHT SCATTERING
As each cell passes through the s ensing zone, it scatters light. Scattered light is converted into an electrical pulse.
LIGHT SCATTERING
LIGHT SCATTERING
Number of pulses is directly proportional to
cell count
LIGHT SCATTERING
Patterns of scatter are measured at various angles to obtain information on the
cell structure.
Dilutions :
WBC= (?) (usual dilution, but may vary among manufacturers)
RBC=
1:500
1:50,000
graphic representation of cell size versus cell frequency
HISTOGRAMS:
produced in RBC, WBC & platelet measurements
HISTOGRAMS:
Derived from the histogram are
blood Indices as well as WBC differential
RBC histogram:
36 360 fL
It IS where MCV & RDW are derived
RBC Histogram
Histogram appears (?) when cell population is (?) if there is more variation in the size of the cell
SYMMETRICAL/Gaussian shape
homogenous WIDER or FLATTENED shape
Platelet histogram:
2 - 20 fL
Where MPV & PDW are derived
PLATELET Histogram
(used in the 3-parameter Differential count)
WBC Histogram
WBC Populations on the histogram
35 - 90 fL:
90 - 160 fL:
160 - 450 fL:
Lymphocytes
Mononuclears (Mid cells) - (Monocytes, Promyelocytes,
Myelocytes, Blasts)
Granulocytes - (Mature WBC, Blasts, Metamyelocyte, Bands)
a visual display of 2-cell characteristics such as internal cell complexity and relative size
SCATTERGRAM / CYTOGRAM / DOT PLOTS
It is used in the 5-part automated differential.
SCATTERGRAM / CYTOGRAM / DOT PLOTS
SCATTERGRAM / CYTOGRAM / DOT PLOTS
Cytochemical stains
Peroxidase:
Alcian blue/Toluidine blue:
Lipase/Esterase:
PMN & other cells
basophil
monocytes
What are the indications of histograms with left elevation? with right elevation?
What are the bases of separation of cells in a scattergram? _________________________ _________________________
WBCs are differentiated into 5 traditional categories
Cyanmethemoglobin principle
HEMOGLOBIN
HEMOGLOBIN
At what wavelength? ________
Indirect method (calculated)
HEMATOCRIT
HEMATOCRIT
What is the formula? ________
MCH & MCHC are calculated from measure & derived values
RDW
INDICES
From where is RDW derived? ________
INDICES
Aperture plugs
Causes of POSITIVE errors
Extraneous electrical pulses (improperly grounded or shielded equipment)
Causes of POSITIVE errors
Bubbles in the sample (vigorous mixing)
Causes of POSITIVE errors
Improper setting of aperture current or threshold
Causes of POSITIVE errors
Agglutinated red cells or platelets
Causes of POSITIVE errors
Excessive lysing of RBCs
Causes of NEGATIVE errors
Improper setting of aperture current or threshold
Causes of NEGATIVE errors
Agglutination of RBCs, WBCs or platelets
Causes of NEGATIVE errors
a quality control check in which the averages of the MCV, MCH, MCHC are tracked for batches of 20 patients
XB
Patients test results are compared to his previous results
Delta Checks
: suggest cells types/abnormalities
Flags
indicate investigation before final reporting.
Flags
What are the causes of falsely increases and falsely decreased automated cell counts? – RBC, WBC & Platelets (Henry’s Clinical Diagnosis and Management by Laboratory Methods)
What conditions may affect automated hemoglobin measurement? Explain each
(What are the indications for)/When should we perform a manual peripheral blood smear review?