Smudge cells percentage on blood smear is a reliable prognostic marker in chronic lymphocytic leukemia

Abstract

Objective: We evaluated the relevance of using the smudge cell percentage in the blood smear as a prognostic marker in CLL.

Methods: In this prospective study, 42 untreated Senegalese patients with CLL were enrolled. The diagnosis was established, based on the peripheral blood count and flow cytometry using the Matutes score. Cytogenetic aberrations, assessed by fluorescence in situ hybridization (FISH), were available for 30 patients, while the immunoglobulin heavy chain genes (IGVH) mutation status was performed by next-generation sequencing (NGS) in 24 patients. The SC percentage was determined in the blood smear, as previously described. Statistical analyses were executed using the GraphPad Prism 8.

Results: The mean age was 63 years (48 - 85) and the male: female sex ratio was 4.66. A low SC (< 30%) percentage was correlated with Binet stage B/C (p = 0.0009), CD38 expression (p = 0.039), unmutated IGVH status (p = 0.0009) and presence of cytogenetic abnormalities (for del 13q, p = 0.0012, while for other cytogenetic aberrations, p = 0.016). An inverse correlation was found between the SC percentage and the absolute lymphocyte count (r = -0.51) and patients with higher percentage of SCs had a prolonged survival. However, there was no correlation between the SC percentage and age (p = 0.41) or gender (median, 19% for males vs. 20% for females; p = 0.76).

Conclusion: When less than 30%, the SC was associated with a poor prognosis in CLL. Easy and affordable, the percentage of SCs in a blood smear could be a reliable prognostic marker, accessible to all CLL patients, mainly those in developing countries.

Keywords: Blood smear; CLL; Prognostic marker; Senegal; Smudge cells.