CD79A and myeloid sarcoma: Kappa index, on the other hand, supplies quantitative information, which may be useful “per se” (very high kappa index values have been found virtually only in MS), and may capture signs of intrathecal synthesis of other immunoglobulin classes (such as IgM and IgA), which are not detected when searching for IgG OCB and, thanks to its higher sensitivity, it may be useful as a support to the diagnosis of other CNSID, in which intrathecal synthesis may be less “full-blown” than in MS.