Automation hematology Flashcards
BASIC COMPONENTS OF MOST HEMA ANALYZERS
Hydraulics, Pneumatics, Electrical systems
Aspirating unit, dispensers, dilutors, mixing chambers, aperture baths, flow cells, hemoglobinometer
Hydraulics in HEMA analyzers
Vacuum and pressure systems for operating valves and moving samples
Pneumatics in HEMA analyzers
Electrical systems in HEMA analyzers
Electronic analyzers, computing circuitry for data processing
ELECTRICAL IMPEDANCE principle
Cell counting
Origin of Electrical Impedance
Developed by Coulter in the 1950s
Most common methodology for cell counting
Electrical Impedance (Coulter Principle)
Radiofrequency (RF) in electrical impedance
Modification of DC impedance, measures conductivity, AKA alternating current
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
Impedance change during cell passage
Caused by non-conductive particles (cells) in an electrically conductive diluent
Pulse generation in electrical impedance
Proportional to the number of cells passing through the aperture
Pulse amplitude in electrical impedance
Indicates the cell’s volume
Radiofrequency (RF) in electrical impedance
Measures conductivity and changes in RF signal reflect cell interior density
Two-dimensional distribution cytogram
Plots RF conductivity and DC impedance of cells
Scatterplot in electrical impedance
Displays clusters of cells, representing concentration of a specific cell type
Also known as Electronic Resistance or Coulter Principle
Electrical impedance
Instrumental Error: Most common problem in cell counting, produces POSITIVE (+) ERROR
Aperture plugs
Instrumental Error: Caused by too vigorous mixing, produces POSITIVE (+) ERROR
Bubbles in the sample
Instrumental Error: Produces POSITIVE (+) ERROR
Extraneous electrical pulses
Instrumental Error: Produces NEGATIVE (-) ERROR
Excessive lysing of RBCs