Rapid and simple immunophenotypic characterization of lymphocytes using a new test.

BACKGROUND AND OBJECTIVE: In this paper, we report our experience of lymphocyte phenotyping of a series of 108 consecutive samples using a simple flow cytometry test (Lymphogram). The kit consists of a combination of 5 different markers conjugated with three fluorochromes (CD8-FITC, CD19-FITC, CD56-PE, CD3-PE, CD4-PECy5) in the same tube. This allows identification of different T-cells, NK subpopulations and B lymphocytes.

DESIGN AND METHODS: The samples were divided into three groups: samples with absolute lymphocytosis (> 5 x 10(9)/L) (n = 50), samples with relative lymphocytosis (> 50%) (n = 24) and other categories for which a lymphocyte immunophenotype was required (T-cell lymphoma and estimation of blood involvement in chronic lymphoproliferative disorders (CLPD) (n = 34). When CD19+ cells exceeded the normal range or there was a suspicion of CLPD without B-cell lymphopenia, clonality was investigated by means of light chain restriction analysis.

RESULTS: In the first group, 29 samples were abnormal (10 CLPD, 3 polyclonal B-cell lymphocytosis, 13 inversions of the CD4/CD8 ratio and 3 cases with CD4 lymphocytosis) and 21 samples were regarded as normal. In the second group 7 samples showed abnormalities (2 CLPD, 3 inverted CD4/CD8 ratios and 2 with a relative increase in CD4 cells). In one sample from the third group B-cell clonality without lymphocytosis was detected whereas in 18 samples a polyclonal pattern was observed. The presence of B-cell lymphopenia precluded further clonality study in 13 samples.

INTERPRETATION AND CONCLUSIONS: Lymphogram associated with clonality analysis is a rapid, easy and cheap method of assessing lymphocyte phenotypes in the majority of clinically relevant situations.