# The Impact of Surface CD20 Expression and Soluble CD20 Levels on In Vivo Cell Fragility in Chronic Lymphocytic Leukemia

## TL;DR

This study explores how CD20 levels on and inside CLL cells relate to cell fragility, finding inverse correlations that could help predict disease severity.

## Contribution

The study reveals novel inverse correlations between smudge cells and both surface and soluble CD20 in CLL patients.

## Key findings

- Smudge cells inversely correlate with soluble CD20 levels (r = -0.51, p = 0.006).
- A cut-off of 2.2 ng/dL for soluble CD20 predicts higher smudge cells with 69% sensitivity and 86% specificity.
- Smudge cells also inversely correlate with surface CD20 MFI (r = -0.36, p = 0.04).

## Abstract

Background: Patients with chronic lymphocytic leukemia (CLL) who were not receiving treatment were included in this experimental prospective correlation study. We aimed to elucidate the complex relationship between smudge cells, surface CD20, and soluble CD20 in CLL patients. Methods: We created blood smears from blood samples collected from our patients using a manual technique consistently performed by the same technician. The May–Grunwald Giemsa dye was used to stain all of the slides. The B-cell phenotypic was analyzed using the FacsCanto II flow cytometer (Becton Dickinson, CA, USA) at the time of diagnosis. Competitive Enzyme-Linked Immunoassay (ELISA) was used to quantitatively assess the amounts of soluble CD20/MS4A1. Results: The percentage of smudge cells and soluble CD20 antigen levels were shown to be significantly inversely correlated, suggesting a considerable link (correlation coefficient (r) = −0.51, p = 0.006). Similarly, a significant inverse relationship (r = −0.36, p = 0.04) was found by the Spearman correlation test between the smudge cell ratio and CD20 median fluorescence intensity (MFI) on cell surfaces. Soluble CD20/MS4A1 and surface CD20 MFI were shown to have a weakly positive association that was almost statistically significant (Spearman’s rho = 0.34, p = 0.064). With a sensitivity of 69% and specificity of 86%, we discovered that a cut-off value of 2.2 ng/dL for soluble CD20 predicted higher smudge cells (area under the curve (95% confidence interval (CI)): 0.75 (0.57 to 0.93), p = 0.021). Conclusions: We found a significant inverse association between smudge cells and both surface CD20 and soluble CD20/MS4A1 in our study examining the correlation between smudge cells, soluble CD20, and CD20/MS4A1 in CLL patients. Our findings indicate that soluble CD20 may contribute to understanding the pathophysiology of smudge cells and could be further investigated as a potential prognostic marker in CLL.