Clinlab Navigator

Plasma Cell Enumeration by Flow Cytometry

A study published this month in Archives of Pathology and Laboratory Medicine (2007;131:951-55) showed that flow cytometry may considerably underestimate the percentages of plasma cells in bone marrow specimens compared to morphologic evaluation of aspirate smears.

In an effort to characterize the accuracy of flow cytometry in detecting and quantitating neoplastic plasma cells, researchers from the Department of Pathology at the University of Utah analyzed 30 bone marrow specimens from patients with plasma cell dyscrasias and compared plasma cell percentages determined by flow cytometry to those obtained by morphologic evaluation of aspirate smears. In all but 2 cases plasma cell percentages determined by flow cytometry were markedly decreased compared to diagnostic aspirate specimens. A sample of plasma cell dyscrasia cases from our laboratory during the past year showed similar results as seen in the following table.

Case

Morphologic % Plasma Cells

Flow Cytometry % Plasma Cells

1

49

19

2

46

30

3

35

1

4

17

5

5

15

1

6

12

3

7

11

2

8

9.5

2

Hemodilution of flow cytometry specimens is often cited as the primary cause for underestimation of plasma cells by flow cytometry. However, the University of Utah article suggests that the ammonium chloride solution used to lyse red blood cells may also destroy plasma cells. Further study is warranted.

Although it appears that quantitation of plasma cells by flow cytometry is not completely reliable, the authors of this study maintain that flow cytometry is still useful for determining plasma cell clonality and for providing a lower limit estimate of plasma cell percentages. These applications are particularly valuable in cases submitted for evaluation of residual disease.

AddThis Social Bookmark Button