Method Description

Flow cytometric immunophenotyping of bone marrow is performed using the following antibodies: CD19, CD38, CD45, CD138, cytoplasmic kappa and lambda immunoglobulin, and DAPI (4',6-diamidino-2-phenylindole). Plasma cell clonality is detected through demonstrating CD38 and CD138 positivity along with immunoglobulin light chain restriction (ie, the presence of either predominately kappa or lambda immunoglobulin light chains) and abnormality of CD19 and/or CD45 expression. DNA index of clonal plasma cells and their proliferation activity is determined through staining of double-stranded DNA using DAPI.

Plasma cells (monoclonal/monotypic and polyclonal/polytypic) are detected by immunoglobulin light chain restriction, surface immunophenotype, and DNA content. If present, the light chain expressed by the monotypic plasma cells is indicated. The percentage of clonal plasma cells estimated by flow cytometry is affected by specimen processing and antigen loss with specimen aging. Manual differential counting remains the accepted standard for determining the bone marrow plasma cell percentage. The percentage of monotypic plasma cells in S-phase of the cell cycle is determined by quantitative DNA analysis. The DNA index is a calculated value. The presence of more than 1 value indicates the presence of cell populations with differing DNA contents within the monotypic plasma cells.(Dispenzieri A, Buadi F, Kumar SK, et al. Treatment of immunoglobulin light chain amyloidosis: Mayo Stratification of Myeloma and Risk-Adapted Therapy (mSMART) Consensus Statement. Mayo Clin Proc. 2015;90(8):1054–1081. doi:10.1016/j.mayocp.2015.06.009)

Plasma Cell Proliferative Disorder:

This test is performed using commercially available and laboratory-developed probes. Deletion or monosomy of chromosome 17, copy number gain of 1q, and additional copies of chromosomes 3, 7, 9, and 15 are detected using enumeration strategy probes. Translocations involving IGH are detected using dual-color, dual-fusion fluorescence in situ hybridization strategy probes. Rearrangement of IGH and MYC are detected using a break-apart strategy probe. For each probe set, 50 plasma cells (if possible) are scored and the result for each probe is reported. (Unpublished Mayo method)

Minimal Residual Disease:

Flow cytometric immunophenotyping for minimal residual disease of bone marrow is performed using the following antibodies:

Tube 1: CD138, CD27, CD38, CD56, CD45, CD19, CD117, and CD81.

Tube 2: CD138, CD27, CD38, CD56, CD45, CD19, cyKappa, and cyLambda.

Abnormal plasma cell populations are detected through demonstrating CD38 (multiepitope) and CD138 positivity along with immunoglobulin light chain restriction (ie, the presence of either predominately kappa or predominately lambda light chains) and abnormality of CD56, CD117, CD27, CD81, CD19 and/or CD45 expression. The percentage of clonal plasma cells estimated by flow cytometry is affected by specimen processing and antigen loss with specimen aging. Minimal residual disease reporting is affected by sample volume and cellularity.(Unpublished Mayo method)