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Comparison of laboratory methods for the detection of neoplastic plasma cells in plasma cell dyscrasias
  1. Robin Dietz1,
  2. Trang K Lollie2,
  3. Tracie Goh2,
  4. Nagesh Rao2,
  5. Sheeja Pullarkat2
  1. 1 Pathology and Laboratory Medicine, Olive View- UCLA Medical Center, Sylmar, California, USA
  2. 2 Pathology and Laboratory Medicine, UCLA Medical Center, Los Angeles, California, USA
  1. Correspondence to Dr Sheeja Pullarkat, Pathology and Laboratory Medicine, UCLA Medical Center, Los Angeles CA 90095, California, USA; spullarkat{at}


Aims To compare the ability of immunohistochemistry (IHC), multiparameter flow cytometry (MFC) and fluorescence in situ hybridisation (FISH) to detect clonal plasma cells. We also attempted to outline a testing strategy for monitoring multiple myeloma patients.

Methods A retrospective review was performed on 278 CD138+sorted FISH studies from November 2019 to December 2020 along with their concurrent IHC and MFC results. A p value was computed using McNemar’s test for paired data. Association was calculated using the non-parametric Spearman correlation coefficient.

Results Using the Mc Nemar’s test for paired data, CD138+sorted FISH studies achieved the highest proportion of positive results and was significantly greater than MFC (63% vs 53%, p=0.01). FISH had more positive results than IHC, although this did not reach statistical significance (60% vs 57%, p=0.34). IHC and MFC had high correlation and high agreement (90.3% agreement, kappa=0.805, p<0.0001). CD138+sorted FISH studies achieved the highest proportion of positive results relative to IHC and MFC, indicating that it may be a reliable marker for clonal plasma cell detection.

Conclusions While CD138+sorted FISH is primarily used for prognostication, it may be employed as a single test for detection and monitoring clonality in certain scenarios. Further studies are needed to monitor the outcomes of patients with positive FISH and negative IHC and MFC. Additionally, there was high agreement between IHC and MFC, suggesting that performing both tests may not be necessary.

  • Multiple Myeloma

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  • Handling editor Runjan Chetty.

  • Contributors RD: conduct, reporting, acquisition of data and analysis and interpretation of data, initial draft. TKL: conduct, reporting, analysis and interpretation of data. TG: data analysis and interpretation of data. NR: data analysis and interpretation. SP: planning, conception and design, conduct, reporting, manuscript preparation.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.