A clinical lab analyser is a machine that measures what is in a sample of blood or urine, automatically and in large numbers. Hospital labs and reference labs use several kinds. A clinical chemistry analyser measures substances such as sugar, cholesterol and creatinine, a waste product that shows how well the kidneys work. An immunoassay analyser measures hormones, such as thyroid hormone, and antibodies, the proteins that the body makes against an infection. A haematology analyser counts the blood cells. Large labs join these machines with conveyors. This is called lab automation.
Chemistry and immunoassay analysers work in the same basic way. A robotic arm takes a tiny amount of the sample, often a few microlitres, from the tube. It mixes the sample with a chemical called a reagent, which reacts with the substance being measured. The reaction changes the colour of the mixture, or makes it give off light. A light sensor measures the change. The analyser then converts that measurement into a result, such as a creatinine level in milligrams per decilitre (mg/dL). A haematology analyser works differently. It passes the cells one by one through a very narrow opening and counts them by size and type.
An analyser is accurate only if it is checked. Every morning, before the patient samples, the lab runs control samples whose values are already known. If a control gives the wrong value, the lab stops and recalibrates the machine. This is called quality control. Labs accredited by NABL, India's accreditation board for testing laboratories, must keep a record of every such check.
For instance, the lab of a 500-bed hospital in Mysuru receives about 1,500 tubes on a busy morning. Each tube goes onto the conveyor. A scanner reads its barcode and asks the laboratory information system (LIS) which tests the tube needs. The conveyor removes the cap and sends the tube first to the chemistry analyser for a kidney test, then to the immunoassay analyser for a thyroid test. The chemistry analyser measures the creatinine at 1.1 mg/dL, inside the normal range, and sends the result to the LIS. The tube is then capped and stored in a fridge, in case the doctor asks for another test later. A routine result is ready in about an hour.
The analyser's built-in software, its firmware, controls the arms, the timing and the sensors. The maker also sells the reagents, and over the years a lab usually spends more on reagents than on the machine. So makers often place a machine in a lab at a low price and earn from the reagents. The same machines run in hospital labs and in the central labs of reference laboratories. A small analyser used beside the patient is a form of point-of-care testing. A machine that looks for a germ's genes instead is a molecular test system.