Smudge Cells in Chronic Lymphocytic Leukemia: Pathophysiology, Laboratory Considerations, and Clinical Significance.

Abstract

Chronic lymphocytic leukemia (CLL) is the most commonly encountered leukemia in the clinical laboratory. Cytoskeletal defects in CLL lymphocytes can result in the formation of up to 75% smudge cells (SCs) during blood film preparation. Failure to account for these damaged lymphocytes in the white blood cell (WBC) differential diminishes the accuracy and reproducibility of the results. Lacking clear practice standards on handling SCs in CLL, different laboratories may employ different methods to mitigate SC-induced errors. This review explores the pathophysiology of SCs, their effect on WBC differentials in CLL, and how these results can impact clinical decisions. The pros and cons of various SC corrective methods are described to assist laboratories in developing an optimized protocol to reduce errors and inconsistencies in WBC differentials. Finally, the potential utility of SC enumeration as an indicator of CLL prognosis is discussed in terms of laboratories with differing access to technology.