Concordance between flow cytometry CLL scores.

INTRODUCTION Multiple flow cytometry scores/diagnostic systems for the classification of leukemic lymphoproliferative disorders (LPD) have been published but few have been compared between them. PATIENTS AND METHODS We classified a cohort of leukemic LPD based on eleven published flow cytometry scores/diagnostic systems and compared their classification as chronic lymphocytic leukemia (CLL) or non-CLL LPD. RESULTS 329 patients were included. Patients classified as CLL ranged from 46% to 73%, depending on the score/diagnostic system used. All eleven scores/diagnostic systems agreed in 184/324 (57%) of patients while in 58/324 (18%) at least two scores/diagnostic systems classified the patient differently (from the majority). Fleiss kappa was 0.74, but pairwise agreement was variable (Cohen's kappa: 0.48 to 0.87). CONCLUSION This study found a suboptimal agreement between published flow cytometry scores/diagnostic systems for the classification of LPD.