Electronic blood analysers Flashcards
Describe biochemistry analysers
Measure various biochemical substances within the blood e.g. glucose, total protein, blood urea nitrogen, creatinine etc.
Describe haematology analysers
Automatically determine total red and white blood cell counts, differential white blood counts, packed cell volume and platelets counts etc
Describe electrolyte analysers
Measure plasma electrolyte levels e.g. sodium, chloride, potassium, bicarbonate etc
Describe hormone analysers
Measure blood hormone levels. Commonly carried out at commercial laboratories but thyroxine and cortisol test kits are now available for diagnosis of hyperthyroidism, Cushing disease etc within vet lab
What are the advantages of automated blood analysers?
Accurate and easy to use
Rapid results for diagnosis of emergency cases
Test kits and reagents are easily obtained
Rapid results and minimal skill required to operate
Minimal degree of calibration and quality control required to ensure data is accurate.
Reliable and comprehensive technical and educational support available from equipment provider
Fast, reliable method of blood examination
Minimise technician error and time require to perform test
What are the disadvantages of automated blood analysers?
Numerous machines available each with a very different technique. Manufactures recommendations should be adhered to for each machine
Errors are common with haematology analysers due to the fragility of blood cells etc therefore supporting results with manual testing is often performed
What are the three types of automated haematology machines?
Quantitative Buffy Coat (QBC)
Impedance counter machines – More accurate
Laser Cell counters – More accurate
Describe Quantitative Buffy Coat Analyser’s (QBC)
Provide:
Total and differential white blood cell counts
Total red blood cell counts
Whole blood pipetted into microhaematocrit tube and float added
Sample spun in centrifuge to separate sample
Float separates buffy coat into constituent cell layers which are measured accordingly
Provides a granulocytes count and a combined mono and lymphocyte count in addition to red blood cell count
Describe impedance counter machines
Measures electrical resistance (impedance) as cells pass through a small aperture.
Each time a cell impedes a current a pulse is produced
Cell counts are determined by the number of pulses measured in a given volume of blood over a set period of time.
Size of pulse is proportional to size of cell
Produces large numbers of parameters and accompanying graphs. Some machines also give white cell differentials.
Describe laser cell counters
Laser detection systems is used to detect the reflectance, transmission and scattering of light by cells
Each cell is analysed by sophisticated software giving a numerical representation of the likely overall distribution of cell populations.
Provides larger numbers of parameters to illustrate cell distribution for red cells, white cells and platelets.
Produces white cell differentials using peroxidase staining, measurement of cell size and nuclear density.
Describe dry chemistry analysers
Reagents are provided on impregnated slides or pads
Serum sample is placed on to the pad and inserted into the machine
The machine determines the assay to be performed by reading a bar code on the slide
A colour change on the pad commonly occurs, the degree of colour change is proportionate to the solution concentration
The solution concentration is measured and generated as a digital reading or result
Most commonly used
Idexx Vet Test chemistry analyser
Catalyst Dx chemistry analyser
Describe wet chemistry analysers
Uses small wells of fluid instead of dry slides
Generates specific wavelengths
light is passed through a liquid sample
The intensity of the emergent light is measured, converted into electrical energy and displayed digitally
Multiple samples can be analysed at one time
Multiple chemical tests can be performed at one time
Improved accuracy of results
Specific maintenance requirements
Chemical reagents
Daily calibration
Cleaning etc
Describe automated electrolyte analysers
Electrolytes are generally measured by flame photometry in the large commercial laboratories (NaCl (orange) KCl (purple)
Smaller versions used in practice use ion-sensitive electrodes.
An electrical current is passed through a specific ion-sensitive electrode bathed in a chemical and the measurement of the charged particles is taken.
The commonest electrodes used in practice are sodium, potassium and chloride.
Sample quality, particularly haemolysis can strongly affect the results and should be taken into consideration
