PB2065 DIAGNOSTIC VALUE OF THE NEW SYSMEX XN 2000 AUTOANALIZER IN THE STUDY OF LYMPHOCYTOSIS
Authors: Díaz F. , Awol R. , Onate G. , Sabtaliestra M. , Remacha A. 
Published: June 2019

Background:

The new Sysmex analyzers of the XN series (Sysmex Corporation, Kobe, Japan) incorporate new leucocytes channels (WNR, WPC or WDF) based on fluorescence flow cytometry. Fluorescence flow cytometry, through these channels, enables separation of different leukocyte populations and generates numerous cellular parameters. The FSC (forward light scatter) intensity is proportional to the cell size, the SSC (side light scatter) to cellular complexity (granularity) and the SFL (lateral fluorescent light) to DNA/RNA content of the cells (nucleus). Several flags (QFLAGS) alert of blasts, abnormal (ABN) lymphocytes (neoplastic) and atypical (ATYP) lymphocytes (reactive) have been developed based on the cells scatter light behavior. High fluorescence lymphocytes (HPLC) can also be quantified. Moreover, Syxmex XN analyzers incorporate non‐routine parameters, such as those of the lymphocyte populations: three related to the midpoint LY‐X (the lateral scattered light intensity), LY‐Y (the fluorescent light intensity), LY‐Z (the FSC intensity); and three with the distribution area LY‐WX (the lateral scattered light distribution width) LY‐WY (the fluorescent light distribution width) and LY‐WZ (the FSC distribution width). In a previous study, we observed that the lymphocyte parameters and the alarms of Sysmex‐XN (age, number of lymphocytes, Q‐FLAG, LY‐Z, and LY‐WZ) are useful tools to guide the diagnosis of lymphocytosis with an overall diagnostic value 87%1.

Aims:

To determine the diagnostic value of these parameters obtained in a previous study 1in a different population of lymphocytosis.

Methods

217 new cases with lymphocytosis > 4.0 × 109/l were recruited. A peripheral blood immunophenotype (IF) was performed to distinguish polyclonal (n = 144) and monoclonal (n = 73) lymphocytosis. This study also allowed the separation of 33 cases of chronic lymphatic leukemia (LLC), 18 cases of LLC zap70 + and 22 marginal lymphomas.

All the samples were analyzed with the XN‐2000 for WDF and WPC channels. The diagnostic value of the statistically significant variables obtained from a previous study 1, including Age> 60 years; Lymphocytes> 7 × 10E9/L and> 12 × 10E9/L; QFLAG ATYP + ABN> 205 and> 345; LY‐Z> 64,> 65 and> 67; LY‐WZ> 590 were applied in this new group of samples.

Results:

When we consider age (60years) as a cut‐off point, in the group <60 years we only observed 3 cases with monoclonal lymphocytosis, which was considered unrepresentative.

In the group >60 years we observed 71 polyclonal and 70 monoclonal lymphocytosis (table). XN‐based parameters showed a global classification value of 83%. Regarding monoclonal lymphocytosis, 54 of the 70 patients (77%) were correctly classified. The most predictive variables of clonal lymphocytosis were QFLAG ABN + ATYP (PPV 83%) and absolute lymphocyte count > 7 × 109/L (PPV 72%).

Summary/Conclusion:

The results were similar to our previous study and confirmed the utility of these parameters in an initial study of lymphocytosis. The positivity of these variables had a high predictive value of monoclonal lymphocytosis. Therefore, it could be used as a routine practice in laboratories.

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