Using Smudge Cells Percentage on Routine Blood Smear in Chronic Lymphoytic Leukemia As Prognostic Factor: Senegalese Experience
Authors: Sall Abibatou , Touré Awa Oumar , Sall Fatimata Bintou , Sène Abdoulaye , Aumont Cedric , Seck Moussa , Faye Blaise Félix , Dièye Tandakha Ndiaye , Diop Saliou , Reynaud Sophie , Raphaël Martine 
Published: November 2019

Introduction/ Background : Chronic lymphocytic leukemia (CLL) is a heterogeneous disease which can present as an aggressive and life threatening leukemia or as an indolent form that will not require treatment for decades. This heterogeneity has important consequences which will impact on clinical approaches, treatment strategies, and survival times from diagnosis. Prognostic markers such as expression of specific proteins in or on CLL cells (ie, CD38, 70-kD ζ-associated protein or CD49d), cytogenetic abnormalities (del 13q, del 11q, del 17p and trisomy 12) quantified by FISH and immunoglobulin heavy chain (IgVH) gene mutation have all been very useful. Futhermore, patients with early-stage disease, with biologically aggressive disease and shorter survival times can be distiguished. However, these prognostic tests are expensive and require considerable technical expertise and equipment and thus are not available to many patients with CLL living in developing countries. Therefore less expensive prognostic markers are needed. In this study, we evaluated the prognostic significance of smudge cells percentage on a blood smear in CLL patients.

Patients and Methods : In this prospective study, 42 untreated patients with CLL have participated after signing a consent form. Patients were seen at our center between July 2011 and May 2015. Patients were diagnosed on the basis of an absolute lymphocyte count greater than 5.109/L and a demonstration of monoclonality using flow cytometry (panel comprising CD19, CD5, CD22, CD23, FMC7, and surface Ig). Staging was done according to the Binet staging system. CD38 surface expression was determined by flow cytometry in all patients. The cytogenetic abnormalities : del 13q, del 11q, del 17p and trisomy 12, were performed by FISH and available for 25 patients.Smudge cells were defined as broken cells with no intact cytoplasm and a disrupted nuclear membrane (Figure 1). The smudge cell percentage is estimated by counting 200 lymphocytes and/or smudge cells; the smudge cell number is then divided by total number of cells counted (smudge cells + intact lymphocytes) and multiplied by 100. Each slide was evaluated by 2 hematologists and the blood smears were prepared using a manual wedge method. Categorical variables were analyzed using the χ2 test or Fisher exact test (p<0.05). The statistical analysis was performed using STATA version 13.

Results : The mean age was 63 years ranging from 48 to 85. There were 31 males and 11 females (sex ratio=2.81). At the time of diagnosis 81% of the patients were classified as having advanced Binet stages B or C. The median lymphocyte count was 189.9 109/L (ranges, 5.2 - 887 109/L). The prognostic marker CD38 was positive in 28 patients, while 11 patients had 13q del, 7 patients Trisomy 12, 3 del 11d and 3 del 17p. The median smudge cell percentage was 20.1% (range, 4 - 80%) and 30 patients had a percentage less than 30. We found no correlation of proportion of smudge cells with age (p=0.19) and sex (p=0.76). However there was a significant correlation with the Binet stage (p=0.0002), the CD38 expression (p=0.04) and a negative correlation with the lymphocyte count (p=0,01) (r= -0,38).

Conclusion:

A low percentage of smudge cells (less than 30%) is associated with high lymphocyte count, advanced Binet stage (B or C) and positive CD38. Simple, accessible and inexpensive, the percentage of smudge cells on a routine blood smear could be a prognostic test available to all patients with CLL especially those in countries with limited resources.

Figure 1. Blood smears of patients with CLL. A, B, C : presence of smudge cells (arrows). D : blood smear without smudge cells. Figure 1. Blood smears of patients with CLL. A, B, C : presence of smudge cells (arrows). D : blood smear without smudge cells.

Disclosures

No relevant conflicts of interest to declare.