Combination of cellular population data and CytoDiff analyses for the diagnosis of lymphocytosis.

ABSTRACT

BACKGROUND: Differentials with moderate lymphocytosis are common in hematology laboratories and it is important in these cases to discriminate monoclonal from reactive lymphocytosis (RL). Blood smear reflex examination is dependent of the expertise of a cytologist, time-consuming and not always informative. Therefore, rapid and easy orientation parameters are clearly needed to discriminate malignant from RL. METHODS: The differential performed by the Beckman-Coulter analyzers is based on the determination of three parameters (volume, conductivity and scatter of the cell subpopulations) called cellular population data (CPD). This study evaluated CPD in 332 patients with a typical B-chronic lymphocytic leukemia (B-CLL), 90 patients with other B-lymphoproliferative diseases (OLPD) and 55 patients with a proven RL, and established a discriminating protocol to identify these pathologies. Secondly, this approach was evaluated in a prospective study including 102 patients with lymphocyte counts above 3.5 × 10(9)/L and in each case the diagnosis suggested by CPD was compared with conventional flow cytometry (FC) analysis and that obtained using CytoDiff reagent, a combination of six antibodies/five colors which performs a rapid WBC differential by FC. RESULTS: Lymphocyte anisocytosis was observed for malignant and RL. A low lymphocyte volume identifies monoclonal B-cell lymphocytosis and classical B-CLL. CytoDiff analysis is helpful when lymphocyte volume is in the normal range. A ratio B-Ly/total Ly count >0.32 is suggestive of a B-malignancy, whereas a non-cytotoxic T-lymphocyte count above 2.43 × 10(9)/L suggests RL. CONCLUSIONS: The analysis of CPD in combination with CytoDiff analysis shows promise for the rapid and accurate identification of lymphocyte pathologies in routine practice.