Different methods of putting samples through have been invented, but usually involve placing test tubes of sample into racks, which can be moved along a track, or circular carousels that rotate to make the sample available.
Samples can be processed in batches, or continuously.
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2 Immuno-based analysers 3 Haematology analysers |
Routine biochemistry analysers
These are machines that process the bulk of the samples going into a hospital or private medical laboratory. And the results should be out as quickly as possible. There will often be a method that can get urgent specimens moved more quickly through.
The types of tests required are often enzyme levels (such as many of the liver function tests), ion levels (e.g. sodium and potassium), and other tell-tale chemicals (such as albumin or creatinine).
Simple ions are done with ion selective electrodes, that let one type of ion through, and measure voltage differences. Enzymes are measured by the rate they change one coloured substance to another; the results for enzymes are given as an activity, not a concentration of enzyme. Other tests use colorimetric changes to determine the concentration.
Turbidity (as created when an antibody reacts with a test compound) can also be measured with these machines.
Examples of these types of machines are:
The concentration of these compounds is often to low to cause a measurable increase in turbidity when bound to antibody, so other, more specialised, methods must be used.
Examples of these analysers include:
Blood counting machines sample the blood, and pass it through a thin tube, counting the number of cells going past, and calculating their size.
Automated coagulation analysers first add calcium to a sample (which undoes the anticoagulant) then trigger it to clot, measuring the amount of time it takes to do so.
Automatic ESR readers, while not strictly analysers, hold a rack of samples for an hour, then after an hour determine how far the red cells have fallen, by detecting levels with light beams.
Examples of full blood count machines are:
Coagulation machines include: