Automated Test Methods Flashcards
What is the impedance principle
based on the detection and measurement of changes in electrical resistance produced by cells passing through a small aperture
How is cell count determined using impedance
the number of voltage pulses
How is cell size determined using impedance
the length or height of voltage pulses
What method does the Beckman analyzer use
gentle vaccum
What method does the Sysmex analyzer use
hydrodynamic focusing
What is a total vote out
if 2 or 3 repeat counts are mismatched no results are reported
What is a partial vote out
if one repeat count is mismatched, the instrument will flag but results will be reported
What are characteristics of RBC histograms
cells between 36 and 360fL
one main population with a guassian distribution
curve should begin at baseline
smaller population to the right of the main population are cells that have been corrected for coincidence
What are atypical findings in a RBC histogram
more than one cell population
wide distribution
high take off due to interferences of particles approx 36fL
What are characteristics of PLT histograms
cells counted between 2-20fL
curve of best fit is overlaid on raw data
curves start and stop at baseline
What are atypical findings in PLT histograms
curve stops above baseline
fitted curve cannot be drawn
fitted curve does not fit raw data
high take off
What are characteristics of WBC histograms
cells counted larger than 35fL
should start or be really close to the baseline
typically 3 distinct populations
What are atypical findings in WBC histograms
high take off due to interferences
How is hemoglobin measured
spectrophotometry
What does forward scatter determine
size/shape of cell
What does side scatter determine
complexity and granularity of cells
What does fluorescence determine
nucleic acids present in the cell
What is the principle of flow cytometry
cells are focused via hydrodynamically focused sheath of fluid and inserted into the light path one at a time they are hit by a laser and the scatter and passage of light is gathered by photodetection
What parameters are measured in the RBC/PLT bath
RBC and PLT count
What parameters are measured in the WBC bath
WBC count
What happens in the hemoglobinometer of a beckman instrument
lysing reagent contains a cyanide pigment that binds and stabilizes the free hemoglobin the absorbance is measured at 525nm and concentration is calculated using Beers law
Beckman instruments use VCS what is this
volume analysis
conductivity analysis
light scatter analysis
What are the components of the 5 part differential a Beckman instrument does
neutrophils, lymphocytes, monocytes, basophils and eosinophils
How is HCT determined
(RBCxMCV)/1000
How is MCHC determined
HGB/HCT
How is MCH determined
HGB/RBC
What are the components of the 6 part differential a sysmex instrument does
neutrophils, monocytes, lymphocytes, basophils, eosinophils and immature granulocytes
What happens in the hemoglobinometer of a sysmex instrument
hemoglobin is oxidized and SLS is added to form SLS-HGB complex which is measured spectrophotometrically at 555nm
What can cause falsely increased WBC counts
NRBCs, Megakaryocyte fragments, micro megakaryocytes, PLT clumps, giant PLT, RBCs resistant to lysis, microorganisms, fibrin strands
What can cause falsely decreased WBC counts
WBC fragmentation, WBC clumps, very small lymphocytes
What can cause falsely increased RBC counts
very high WBC count, giant PLT, fibrin strands
What can cause falsely decreased RBC counts
cold agglutinins, microcytes, schistocytes, hemolysis
What can cause falsely increased PLT counts
small RBC/WBC, schistocytes, microorganisms, WBC fragments, electronic noise
What can cause falsely decreased PLT counts
PLT clumps, old specimens, giant PLT, PLT satellitism
What can cause falsely increased HGB
lipemia, icterus, hemolysis, high WBC count
What can cause falsely decreased HGB
cells that resist lysis
What can cause falsely increased HCT
high WBC count, giant PLT, fibrin strands
What causes falsely decreased HCT
cold agglutinins, microcytes, schistocytes, hemolysis, excess EDTA
What causes falsely increased MCV
hyperglycemia and hypernatremia, cold agglutinins, old specimen
What causes falsely decreased MCV
excess EDTA
What causes falsely increased MCHC
lipemia, icterus, cold agglutinin, hemolysis, high WBC count
What is coincidence
when more than one cell passes through the aperture at the same time. This can falsely decrease cell counts and falsely increase cell volumes
What does protein build up at the aperture cause
increased resistance which results in falsely low cell counts and falsely elevated cell volumes
