Automated immunoassay analysers.

Abstract

It is a little over 10 years since the ®rst reliable instrumentation became available for the automation of immunoassay. Although automation of assays using radioactive labels had been attempted earlier (e.g. Kemtek 3000 1,2 and Technicon Star 3 systems), cost, complexity or unreliability meant there was limited use of such instruments. Semi-automation of radioimmunoassays was possible using sample processors such as those of Kemble Instruments (now Zenyx Scienti®c Ltd) and Tecan Ltd, but the development of sensitive enzyme, chemiluminescence and uorescence immunoassays opened the way for complete automation of immunoassays. The earliest commercial systems were modular semi-automated analysers from Amersham International Ltd (Amerlite) and Wallac UK Ltd (DELFIA). These systems provided automation of repetitive steps such as pipetting and plate washing. Total automation soon followed, such that in 1994 there were 23 fully automated systems from 19 companies. Some companies modi®ed the design of the sample processor to provide a compact bench-mounted analyser (e.g. the Nichols Advantage), but most companies designed their own systems, either bench-mounted or oor-standing. The ®rst of these were batch analysers (e.g. Boehringer ES300 and ES600, Abbott IMx and the Baxter Stratus), but the more recent analysers are all random-access instruments. Developments in engineering and computerization have enabled precise control over the various immunoassay steps so that shorter incubation times and smaller sample volumes can be used. There have also been improvements in the chemicals used to provide the ®nal signal or colour, and knowledge of the antigen±antibody reaction is greater. As a result, assay times are shorter and throughput higher without loss of sensitivity or precision for most assays. At the same time there has been consolidation of assays so that endocrinology, haematinics, serology and tumour marker assays are available on a single instrument.Moreover, there has now been another signi®cant change in instrument design as manufacturers integrate the automated immunoassay analysers (AIAs) with clinical chemistry analysers and total laboratory automation. At the present time there is little information available on the performance of assays on these systems. In some cases the technology on earlier or smaller instruments is the same and it is assumed that assay performance will be similar (e.g. the Elecsys 2010 and the Roche Modular system), but in other cases a completely new instrument with new assay design is being introduced (e.g. Abbott Architect) and little information outside of the manufacturer’s own data is available.