|LETTER TO THE EDITOR
|Year : 2014 | Volume
| Issue : 4 | Page : 258-259
CD138 expression in plasma cells is volatile and time-lag dependent
Pranav Dorwal1, Rashmi Thakur2, Sangita Rawat2
1 Department of Pathology, Medanta-The Medicity, Gurgaon, Haryana, India
2 Department of Pathology, Indraprastha Apollo Hospitals, New Delhi, India
|Date of Submission||14-Oct-2014|
|Date of Acceptance||18-Nov-2014|
|Date of Web Publication||25-Mar-2015|
Certified cytometrist (ISAC), Department of Pathology, UG Floor, Clinical Labs, Medanta-The Medicity, Sector 38, Gurgaon - 122 001, Haryana
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Dorwal P, Thakur R, Rawat S. CD138 expression in plasma cells is volatile and time-lag dependent. Egypt J Haematol 2014;39:258-9
The role of flow cytometry based immunophenotyping has consistently played a major role in the evaluation of hematological malignancies. Apart from leukemias and lymphoma, plasma cell dyscrasias have also been keenly phenotyped in the last few years, leading to various conventions and meetings for standardization of panels.
CD138 is an important marker for plasma cell identification and has even been recommended to be used as the primary gating marker along with CD38 by European Myeloma Network on multiparametric flow cytometry in multiple myeloma and related disorders . Even the recently published EuroFlow antibody panels have included CD138 as a backbone marker in their suggested plasma cell dyscrasia tube .
While studying the immunophenotyping in bone marrow plasma cell cases, we came across a pattern. We decided to analyze this pattern and found that delay in processing of sample resulted in loss of CD138 expression.
A total of 17 cases were studied for assessing this factor; the time-lag was categorized into three groups - that is, less than 4, 4-8, and more than 8 h. It was observed that all cases that were processed and analyzed within 4 h showed CD138 positivity in all the cases. These cases had median fluorescence intensity (MFI) varying from 618 to 813 with a mean of 767. The cases that were processed and acquired in 4-8 h of aspiration also showed positivity in all cases; however, the expression was dim to moderate. The MFI in these cases varied from 38 to 107, with a mean of 82. The samples that were acquired after 8 h did not show expression of CD138 in any of the cases (mean MFI=6). Our study also demonstrated that the quantitation of plasma cells by flow cytometry always yielded a lower yield as compared with the one performed on morphology. This could be due to hemodilution or similarly loss of CD138 (which we use as a gating marker). Smock and colleagues had published a study in 2007, which echoed similar findings .
Similar findings have been demonstrated by Lin et al. . Reid et al.  have also demonstrated that CD138 expression was lost following freeze-thaw and permeabilization.
This clearly demonstrates that, when CD138 is included as one of the plasma cell markers, it is imperative to process the sample at the earliest possible, as the delay could prove detrimental and lead to false negative CD138 expression. As CD138 has now been widely recommended as the gating marker for plasma cells along with CD38, it is important that delay is avoided in all cases of plasma cell dyscrasias immunophenotyping.
A couple of new markers have come up in recent past that have been claimed to be more robust and stable as compared with CD138. These include CD319 (SLAMF7/CS1) and CD269 (TNFRSF17/BCMA) ; however, these markers are yet to be widely validated and approved by a consortium/association of authority. We would therefore suggest that the sample where plasma cell evaluation is to be undertaken using the gating strategy of CD38-CD138 should be processed and acquired as soon as possible, without undue delay.
| Acknowledgements|| |
The authors would like to acknowledge Ms Manisha Gambhir for her support.
Conflicts of interest
| References|| |
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