Choosing the Right Immunoassay Analyzer

Immunoassay analyzers can be classified into different types according to their mode of use, reagent compatibility, or sampling mode:

• Mode of use:
  • Automatic analyzers: The device automatically mixes the samples with reagents. These models are suitable for analyzing a large number of samples.
  • Semi-automatic analyzers: The operator mixes the samples with the reagents. These models are particularly well suited for analyzing small sample quantities. With semi-automatic analyzers, the operator manages the sequence of tests.

• Reagent compatibility:
  • Open systems: These are compatible with reagents from a variety of brands.
  • Closed systems: These, on the other hand, are only compatible with reagents from the device manufacturer.

• Sampling mode:
  • Random access sampling: The immunoassay analyzer accesses samples randomly, i.e. in no particular order.
  • Continuous-access (or sequential) sampling: Samples are accessed in the order in which they are positioned in the rack.

Randox random access immunoassay analyzer

DiaSorin automatic immunoassay analyzer

Boditech semi-automatic immunoassay analyzer

Immunological tests rely on the ability of an antibody to bind to a specific macromolecule known as an antigen. Immunoassays produce a detectable and measurable signal via a marker in response to this binding. Immunoassay analyzers can be used to test a wide variety of substances, including blood and its components (serum, plasma) and urine. Here are some of the molecules measured during the tests (analytes):

• Proteins:
  • Antibodies: By measuring the amount of specific antibodies in a sample, you can infer the amount of antigens present.
  • D-dimers: These proteins are fragments of fibrin, the main component of blood clots. They appear in the blood when clots dissolve. They are involved in everything to do with inflammatory reactions, particularly in blood vessels.
  • CRP: C-reactive proteins (CRP) are synthesized by the liver when there is inflammation or infection in the body.

• Hormones: Hormone levels can be measured to determine the amount of growth hormones or thyroid hormones present. These assays use antibodies specific to the hormones of interest.

• Tumor markers: Certain proteins serve as tumor markers, and are used in particular for oncology applications.

An immunoassay analyzer can be used in a variety of applications to perform many types of tests, such as:

• Cancer marker screening
• Diagnosing infectious diseases (Covid-19, sexually transmitted diseases, etc.)
• Cardiac analysis
• Tests in the pharmaceutical industry for therapeutic monitoring of drugs
• Drug testing
• Allergy tests (dust mites, pollens, animal dander, food allergens, etc.)
• For research purposes

There are many technical criteria for judging the performance of an immunoassay analyzer, such as versatility, throughput, sample capacity, minimum sample volume, and so on. Here is a list of the main performance criteria:

• Versatility: This refers to the number of different tests the analyzer can perform. The higher the number, the more versatile the analyzer.
• Throughput: The number of tests performed per hour. Depending on requirements and the need to analyze large quantities of samples, it may be preferable to opt for a high-speed analyzer. As a reminder, this criterion cannot be applied to semi-automatic analyzers.
• Sample capacity: This is the number of places on the rack where samples are put.
• Minimum sample volume: This is the smallest amount of sample at which the device can detect the presence of antibodies. The smaller the volume, the more sensitive the device and the higher its performance.
• Number of reagent positions: This is the number of reagents that can be loaded at the same time.
• Reaction time: Here again, depending on your needs, it may be worth opting for an analyzer with a fast reaction time. Some devices offer a reaction time of around ten minutes, with the first results available in around twenty minutes.

An immunoassay analyzer is generally available in three configurations: benchtop, portable, or floor-standing.

• Benchtop immunoassay analyzer: This device is generally compact and is placed directly on the laboratory bench.
• Portable immunoassay analyzer: These are very useful for travel and bedside testing (POC).
• Floor-standing immunoassay analyzer: The most powerful models come in this format and they are designed for high-activity laboratories.

Depending on the brand, the number of tests available, and the type of analyzer, prices can vary from a thousand euros to tens of thousands of euros.

Semi-automatic analyzers are generally less expensive than fully automated models.

The use of an immunoassay analyzer presents certain risks, particularly when conducting the RIA method and handling samples. There are also risks of analysis error.

• Conducting the RIA method: There are health risks linked to the use of radioactive substances.
• Sample handling: Some samples may present a risk of infection and must therefore be prepared with care by laboratory staff.
• Risks of analysis error: If the device is poorly calibrated or insufficiently accurate, this can lead to erroneous diagnoses and ultimately harm patients’ health. Hence the need for a robust quality control system to ensure the reliability of the tests carried out.

A laboratory must have a quality control system with documentation detailing the maintenance of the device.

This is necessary to meet international quality standards (NF EN ISO 15189).