The lab analyser family and its building blocks

Recognise the main families of laboratory analysers, name the building blocks they all share, and use that map to find your way around an unfamiliar machine in the first hour on site.

Many machines, one job

Walk into a hospital laboratory and you will see a row of boxes with different names on them: a chemistry analyser, a haematology counter, an immunoassay system, a blood gas analyser in the intensive care unit, a urine strip reader in the corner, perhaps a coagulation analyser. They come from different manufacturers, they look nothing alike, and the people who use them speak about them in the language of medicine: glucose, creatinine, white cell count, TSH, pH, prothrombin time.

For the engineer they are much more alike than they look. Every one of them does the same job in the same order: it takes a small, measured amount of a patient sample, mixes it with a measured amount of reagent or diluent under controlled conditions, measures a physical signal (light, an electrical current, a voltage, a pulse), and turns that signal into a number using a calibration. Then it washes everything that touched the sample and gets ready for the next one. If you understand that chain, you can find your way around any analyser, including one you have never seen.

This matters because the people who use the analyser will describe faults by their clinical result: potassium is high, the controls are out, the platelets are low. Your job is to translate that back into the chain. A wrong number can come from the sample, from the volume that was pipetted, from the reagent, from the temperature, from the light source, from the calibration, or from the software. Most of this course is about learning to ask which link failed.

The families and what they measure

Clinical chemistry analysers measure substances dissolved in serum, plasma or urine: glucose, urea, creatinine, enzymes, lipids, proteins and many more. Most tests are photometric: sample and reagent react in a cuvette, the reaction produces or consumes a coloured compound, and the analyser measures how much light of a chosen wavelength passes through the cuvette. Many chemistry analysers also carry an ion-selective electrode (ISE) module for sodium, potassium and chloride. Small benchtop systems, such as the BioSystems A25 or the Human HumaStar 300SR, use the same principles as large floor-standing ones; the difference is throughput and automation.

Haematology analysers count and size blood cells. The classic method is impedance counting: cells in a conducting diluent are drawn through a tiny aperture, and each cell briefly changes the electrical resistance, giving a pulse whose height is related to the cell volume. Haemoglobin is measured photometrically after the red cells are broken open with a lysing reagent. Simple three-part counters, such as the Sysmex XP-300, rely on impedance; five-part and larger systems add optical flow cytometry, where cells pass one at a time through a laser beam and the scattered and fluorescent light separates the white cell types.

Immunoassay analysers measure hormones, tumour markers, infection markers and drugs, often at very low concentrations. The test uses antibodies to capture the substance, usually on magnetic particles, then washes away everything else and measures a signal from a label. In chemiluminescence systems such as the SNIBE Maglumi 2000 Plus, the label emits a short flash of light when starter reagents are added, and a photomultiplier counts it. The washing and separation steps make the mechanics more complex than chemistry.

Blood gas and electrolyte analysers measure pH, carbon dioxide and oxygen partial pressures, electrolytes and often glucose, lactate and haematocrit, using electrodes rather than light. They usually stand close to the patient, in intensive care or the operating theatre, and run on whole blood, so they are both clinically urgent and biologically dirty. Some, such as the Instrumentation Laboratory GEM Premier 3000, put all sensors, calibration solutions and waste into a single replaceable cartridge, which moves much of the classic maintenance into the consumable.

Urine analysers read reagent strips optically and, in larger systems, image or count the particles in the sediment. Coagulation analysers detect the moment a plasma sample clots, either mechanically or optically. You will meet them less often in this course, but the same building blocks apply.

The building blocks every analyser shares

Take the covers off any of these machines and you will find the same functional blocks, arranged differently. Learn them as a list, because every fault you will ever see sits in one of them or in the connections between them.

• Sample handling: racks, carousels or tube holders, barcode readers, and sometimes a cap piercer. They decide which sample is which, so a fault here can attach a correct result to the wrong patient.
• Probes and arms: the sample and reagent probes (needles) and the arms that move them in X, Y and Z. Probes usually carry liquid-level detection and collision detection.
• Fluidics: syringes or dosing pumps, valves, tubing, wash stations, diluent and system-liquid supply, vacuum and waste. Lesson 3 is about this block, because it causes more faults than any other.
• Reaction area: cuvettes, a reaction rotor or chamber, mixers, incubators. Volume and timing here decide the chemistry.
• Measurement: a photometer with lamp, filters and detector; an impedance transducer; a flow cell with a laser; electrodes; a photomultiplier for luminescence. Lesson 4 covers these.
• Thermal control: heated rotors or baths, heated probes, cooled reagent compartments, all with sensors and control loops. Almost every reaction depends on temperature.
• Electronics and software: power supplies, motor drivers, sensor boards, the controlling computer, the result database, and the link to the laboratory information system (LIS).

The analyser does not stand alone

An analyser is the end of a chain of utilities, and many calls that sound like analyser faults are utility faults. Most chemistry and immunoassay systems need purified water, often from a water purification unit with its own filters, membranes, storage tank and level sensor. If that unit cannot keep up with the analyser's demand, or its tank reports full when it is empty, the analyser fails in ways that look random. Water quality is specified by the analyser manufacturer and in laboratory water standards; it is not just 'distilled'.

Power quality matters too. Analysers contain sensitive measuring electronics and a computer; dips, surges and poor earthing give corrupted settings, failed start-ups and noisy signals. A dedicated supply and, often, a UPS are part of a normal installation. Electrical safety of the analyser itself, earth bonding and leakage testing, is covered in the Electrical safety course.

Waste has to go somewhere: a drain line, a waste container with a level sensor, or a sealed waste bag. Blocked drains and stuck waste-level sensors stop analysers every day. And the room itself matters: temperature, humidity, direct sunlight on the optics, dust, and vibration from a centrifuge on the same bench. Manufacturers state their installation conditions; read them before you start looking inside the box.

Who does what around an analyser

An analyser has three sets of people around it, and you need to know where your work begins and ends. Laboratory staff run samples, load reagents, run calibrations and quality control, and do the daily and weekly maintenance in the operator's manual. The laboratory is responsible for the quality of its results. In Kazakhstan and Russia it needs a licence for medical activity, and many laboratories are also accredited to ISO 15189 or its national version.

The engineer, whether from the hospital, an independent company or the distributor, keeps the machine mechanically, electrically and functionally sound: repairs, periodic maintenance beyond the operator's tasks, adjustments that the service documentation allows, and verification after work. The manufacturer supplies the documentation, the parts, the software and, for many tasks, the authorisation. Reagents, calibrators and controls are part of the measuring system; on most closed systems they are validated as a set with the analyser.

Two practical rules follow. First, never change assay parameters, calibration factors, reference ranges or result-handling settings on your own; those belong to the laboratory and, where relevant, to the reagent manufacturer. Second, after any work that could affect results, the laboratory decides when patient testing resumes, after its own QC and, where needed, calibration. Your job is to hand the machine back in a known, documented state.

Your first hour with an unfamiliar analyser

Sooner or later you will be called to a model you have never touched. Do not start with the screwdriver. Start by building the map in your head, using the blocks above.

Ask the operators to run one sample while you watch, and follow it: where it is identified, which probe takes it, where it goes, how long it waits, where it is measured, and how the probe is washed afterwards. Open the operator's manual at the maintenance chapter; it tells you what the manufacturer considers wear parts and how often they are cleaned or changed. Look at the error and event log before anything else, and note the dates. Ask when the fault started and what changed then: a new reagent lot, a new operator, a move, a power cut, a water unit service.

Finally, look at the utilities: water, waste, power, room. Ten minutes spent here, before any cover comes off, solves a surprising share of first calls.

On-site checklist

• Identify the analyser family and its measuring principle before arrival.
• Watch one sample travel through the machine and note each building block it passes.
• Read the operator's maintenance chapter: wear parts, cleaning intervals, consumables.
• Open the error and event log first and note dates and what changed.
• Check purified water supply, waste line, power and room conditions against the installation requirements.
• Do not change assay parameters, calibration factors or result settings; they belong to the laboratory.

Check yourself