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Evaluation of an innovative new method for quantitation of plasma cells on CD138 immunohistochemistry
  1. Ethan Gantana,
  2. Nomusa Mashigo,
  3. Ibtisam Abdullah,
  4. Ernest Musekwa,
  5. Robert Lohlun,
  6. Erica-Mari Nell,
  7. Carissa Chetty,
  8. Monalisa Ntobongwana,
  9. Zivanai Chapanduka
  1. Department of Haematology, National Health Laboratory Service, Tygerberg Hospital and Stellenbosch University, Faculty of Medicine and Health Sciences, Cape Town, South Africa
  1. Correspondence to Dr Zivanai Chapanduka, University of Stellenbosch, Stellenbosch, South Africa; zivanai{at}


Aim To compare the frequently used CD138 immunohistochemistry-based method of plasma cell quantitation, to a proposed new method, using interobserver and intraobserver concordance parameters.

Methods Archival CD138 immunohistochemically stained slides made from paraffin-embedded bone marrow biopsies of 33 patients with a confirmed diagnosis of multiple myeloma were used. Light microscopic examination was performed using low magnification lenses (10×) for both the overview estimation method (method A) and the new method (method B), and high magnification lenses (50×), for method B only. For method B, reviewers selected three areas with low, intermediate and high plasma cell densities using 10× lenses. Using a well-defined technique, the 50× lens was then used to count plasma cells as a percentage of all nucleated cells. After blinded relabelling of all the slides, the nine reviewers repeated the plasma cell quantitation using both methods. The plasma cell counts were obtained, and the review times were recorded.

Results Overall intraobserver concordance was comparable for method A (concordance correlation coefficient (CCC)=0.840) and method B (CCC=0.733). Interobserver concordance for method A (intraclass correlation coefficient (ICC)=0.793 and 0.713) and method B (ICC=0.657 and 0.658) indicated high similarity between reviewers. Method A showed poor interobserver concordance (ICC=0.105) at low plasma cell densities.

Conclusions The new method is comparable to the frequently used overview estimation method in terms of intraobserver and interobserver concordance, and cost. The new method has superior interobserver concordance at low plasma cell densities. The new method appears more amenable to digital scanning and analysis.

  • multiple myeloma
  • methods
  • bone marrow
  • immunohistochemistry

Data availability statement

All data relevant to the study are included in the article or uploaded as supplemental information.

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Data availability statement

All data relevant to the study are included in the article or uploaded as supplemental information.

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  • Handling editor Mary Frances McMullin.

  • Contributors ZC and EG conceptualised and designed the study, participated in the experimental phase and wrote the draft protocol and manuscript. All the authors participated in the experimental phase of the study and review of the manuscript. EG coordinated all aspects of the conduct of the study.

  • 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.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.