NEW TRENDS FOR AUTOMATION IN IMMUNOASSAYS

Immunoassays are now an important part of the daily activity of the clinical laboratory, concerning various parameters as hormones, tumor markers, drugs, antibodies, viruses and bacterias. The evolution of the instrumentation in this domain is similar to the one in biochemistry. The requirements may be summarized as follows : non isotopic immunoassays, high throughput, large panel of analytes with a low detection limit, stabilized reagents, full automation with easy calibration and even random access. To fulfill these specifications, many analytical and technological problems have to be solved : - Sample identification, detection, and eventual dilution. - "Reagents" may be liquid solutions, suspensions (latex, magnetic particles, liposomes), fibrous materials, and coated tubes or wells. Each type of reagent induces a specific processing. - Reaction processing needs an incubation step and, in the case of heterogeneous immunoassays, washing and separation steps. The delays of the immunological reaction and of the final signal development will determine the size of the incubator, i.e. the size of the instrument, and the throughput of the system. - Signal measurement of low energy light was improved by reducing artefacts due to matrix and optical cuvets, but also by using photon counting detectors. - Calibration is simplified by automated calculation, memorization and in some case replaced by a "master curve" made by the manufacturer for each reagent lot. Future systems should better take in account the biosafety, help the operator to validate calibration, controls and results, and help to clinical interpretation by associated expert systems.