Analysis of the result of thyroid microsomal particle agglutination test by ELISA

: No accurate method to detect thyroid microsomal (MC) antibody (Ab) in serum has been generalized. In this study, the titer of MC Ab obtained by the method of MC autoantibody particle agglutination (MCPA) was analyzed by enzyme linked immunosorbent assay (ELISA). MC and thyroglobulin (Tg) were prepared from Graves' thyroid. ELISA was done by coating the plate with MC, adding Tg to buffer and using peroxidase-conjugated anti-h IgG. 1) The titer of MCPA correlated with the MC Ab ELISA index in serum without Tg Ab, but it did not in serum with Tg Ab. MC Ab was negative by ELISA while it was positive by MCPA in some of the sera with Tg Ab. 2) When ELISA was done using buffer without Tg, the amount of IgG bound to MC was greater in serum with TGPA: + and MCPA: - than in serum with MCPA: + and TGPA: -. 3) The zone phenomenon observed in MCPA did not always indicate an excess of MC Ab. 4) MC Ab was positive by ELISA in some of the negative MCPA sera obtained from patients with Hashimoto's disease in which diagnosis was confirmed by biopsy. In conclusion, the result obtained in MCPA now in use is strongly influenced by Tg Ab. Furthermore, since binding of Ab to MC is judged by agglutination of particles in MCPA, ELISA is superior in sensitivity and accuracy in detecting MC Ab.