An alternative processing approach to increase CD138 intensity in flow cytometric analysis of plasma cells

Background

Surface median immunofluorescence intensity (MFI) of plasma cells antigens, particularly CD138, by flow cytometry underestimates plasma cell populations when compared with that estimated by morphological assessment on Wright's-stained slides. CD138 MFI using traditional sample preparation methods for flow cytometric analysis is often dim and difficult to interpret due to multiple factors. This becomes critical when diagnosing and accurately classifying plasma cell dyscrasias.

Methods

In this study, we analyzed 280 flow cytometric results collected from 2016 to 2022 for CD38 and CD138 MFI on bone marrow aspirates performed by two different methods of sample processing—traditional method of lyse-wash and the alternative method of lyse-no-wash.

Results

Visual examination of histograms showed a clear advantage to CD138 expression intensity with the no-wash method. Although no significant difference was observed in CD38 MFI between the two techniques (p = 0.3), considerable improvement was observed in CD138 MFI with the lyse-no-wash technique of sample processing compared with the conventional method (p = 0.003).

Conclusions

We concluded that the method of lyse-no-wash is superior to traditional methods especially when it comes to handling bone marrow aspirate samples for plasma cell immunophenotyping. This alternate technique increases the sensitivity of flow cytometry to detect plasma cells resulting in bright and crisp signal intensity for surface CD138. This technique may be particularly advantageous when analyzing low tumor burden such as minimal residual disease.