Specificity is the most important aspect of the immunoassays and was evaluated using several techniques.
5.3.1. Immunoelectrophoresis(Figure 5.2)
5.3.2. Western blot analysis
Western blot analysis is a sensitive technique used to assess the reactivity of the antisera against immunoglobulin fragments and FLC polymers. The results showed that both κ and λ FLC antisera reacted strongly, with two closely migrating bands at 25 - 30 kDa, and weakly with several larger and smaller molecular weight fragments. Similar staining patterns were observed using monoclonal antibodies. The FLC antisera were readily able to detect monomers and dimers of both κ and λ molecules (Figure 5.3).
5.3.3. Haemagglutination assays(Figure 5.4).
5.3.4. Nephelometry(Figure 5.5). Nephelometric assays demonstrated that FLC antisera had minimal reactivity with light chains on intact immunoglobulins and other potentially interfering substances (0.2 - 0.01%). These values are within the purity specification for FLC contamination in the tested interfering materials.
There have been no published independent specificity analyses of the nephelometric Freelite latex reagents. Nakano et al.  reported an evaluation but, in error, only tested FLC antisera that were manufactured for immunofixation electrophoresis (IFE), where specificity requirements are less demanding.