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An approach for diagnosing plasma cell myeloma by three-color flow cytometry based on kappa/lambda ratios of CD38-gated CD138+ cells

Shoko Nakayama1*, Taiji Yokote1, Yuji Hirata1, Kazuki Iwaki1, Toshikazu Akioka1, Takuji Miyoshi1, Ayami Takayama1, Uta Nishiwaki1, Yuki Masuda1, Toshiyuki Ikemoto2, Hidema Tanaka2, Yasuichiro Nishimura3, Motomu Tsuji4 and Toshiaki Hanafusa1

Author Affiliations

1 First Department of Internal Medicine (I), Osaka Medical College, 2-7 Daigakumachi, Takatsuki City, Osaka, 569-0801, Japan

2 Central Clinical Laboratory, Osaka Medical College, Takatsuki City, Osaka, Japan

3 Division of Mathematics, Osaka Medical College, Takatsuki City, Osaka, Japan

4 Division of Surgical Pathology, Osaka Medical College, Takatsuki City, Osaka, Japan

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Diagnostic Pathology 2012, 7:131  doi:10.1186/1746-1596-7-131

Published: 28 September 2012

Abstract

Background

World Health Organization (WHO) criteria are commonly used to diagnose plasma cell myeloma (PCM); however, these criteria are complex and require several laboratory parameters. For differentiating reactive plasmacytosis from clonal plasma cell (PC) neoplasms such as PCM, it is important to accurately determine the expression of cytoplasmic immunoglobulin light chains.

Methods

We retrospectively analyzed the records of 27 selected patients with PCM who underwent bone biopsies for confirmative diagnosis according to WHO criteria. Twenty-three controls were also investigated. In the present study, all the samples were analyzed using flow cytometry (FC) in the side scatter vs. CD38 histogram mode, and the CD38-gated PC population was identified. Bivariate histograms of CD138/kappa and CD138/lambda were assessed, and the ratios of dual-positive cells to the CD138+ PC population were calculated. The kappa/lambda ratio was defined as the ratio of CD138/kappa to CD138/lambda.

Results

PCM cells were distinguished from normal PCs using cutoff levels between 0.76 and 1.5, at a sensitivity of 96.3% and specificity of 95.7%.

Conclusions

Three-color FC analysis is simple to perform and inexpensive, with clinically relevant data obtained soon after the completion of FC measurements. The detection of the cytoplasmic kappa/lambda ratio of CD38-gated CD138+ PCs may be a useful tool in the diagnosis of PCM. To the best of our knowledge, this report represents the first diagnostic assessment of the cytoplasmic kappa/lambda ratio in CD38-gated CD138+ PCs using FC analysis. This method may help in more simple, efficient, rapid, and accurate diagnosis of PCM.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1568085959771735

Keywords:
Plasma cell myeloma; Diagnosis; kappa/lambda ratio; CD138; CD38