5.8. Immunoassay development on different platforms

Chapter 5

Freelite assays were initially developed for the Siemens BN™II nephelometer, and following their successful launch in the year 2000, the range of platforms has expanded and the assays are currently available on a total of 10 different instruments. Developing Freelite assays across different platforms poses a challenge as each instrument has unique features (summarised in Table 5.2). These include differences in the optical detection systems and the methods for reagent and sample handling. Therefore, assays developed for each platform may vary slightly in terms of sensitivity, measuring range, precision and antigen excess detection. However, there is good agreement between the sFLC results obtained with the different instruments. An example of κ and λ sFLC results obtained for BNII and SPAPLUS instruments is shown in Figure 5.10.

System feature
Sampling Cuvettes (disposable/semi-disposable/non-disposable), cuvette cleaning method, probes/pipettes
System liquids Wash solutions, sample diluent, tubing and pumps
Reagent storage Compartments and carousels, temperature control (refrigerated/non-refrigerated)
Sample dilution Automatic on-board/manual off-line
Detection system Light source, light detector (nephelometric/turbidimetric)
Channels Open/closed
Software and parameters Sample flags, automatic antigen excess detection
Integration Tracked system/stand-alone, laboratory information system integration

Table 5.2. Features that may vary between different analytical platforms.


  1. How are Freelite assays routinely standardised?


  1. As no international standards exist for FLC measurements, Freelite assays are standardised against κ and λ internal reference materials, which, in turn, are calibrated to highly purified primary standards (Section 5.4).