[Evaluation of samples that indicated the difference of immunoglobulin values between different assays]

Since the immunoglobulin levels of survey samples for the survey of Japanese Association of Medical Tech7ologists in 2003, especially the IgA and IgM, became different by the immunological methods (LAIA [latex agglutination immunoassay] and TIA [turbidimetric immunoassay]), the cause of difference was investigated. From the results of gel filtration and immunoblotting analysis, it was suggested that profiles of the reaction of purified IgA and IgM polymers in survey samples were different on each method. In the case of M protein, also, there were higher levels of IgM and IgA type M protein by TIA and SRID methods than other methods even though the precipitation curve was obscure. Similarly, several samples from patients with M protein demonstrated higher values by SRID method than that of other methods. When these samples were analyzed by gel filtration and immunoblotting, they did not indicate the presence of the polymeric IgM. It will be suggested that non-specific reactions on TIA (weak reaction) and SRID (unusual precipitin line) methods were present. Furthermore, in a case of IgM type M protein, IgM level was twice higher by LAIA than that by TIA. However, it did not indicate any polymer or fragment of IgM by gel filtration and immunoblotting. Accordingly, it was assumed that the difference in measured values between the methods was attributable to the difference of the reaction to the samples.