Quantitative criteria for clonality in the diagnosis of B-cell non-Hodgkin's lymphoma by flow cytometry.

Fifty-three cases of B-cell non-Hodgkin's lymphoma (BNHL) and 41 cases of non-BNHL lesions were retrospectively evaluated for the quantitative features of restricted surface light chain expression, pan B-cell antigens, pan T-cell antigens, and T-helper and T-suppressor phenotype using flow cytometry. Decision limit analyses were applied to multiple quantitative indices of immunophenotype to establish criteria for the detection of clonal proliferation associated with BNHL or non-BNHL conditions. Two data expressions (percent population and relative ratios) were simultaneously analyzed. The percent population measures were amenable to parametric analyses; the ratio data were amenable to nonparametric analyses only. Acceptable diagnostic specificity and sensitivity were obtained using decision limits of 75% kappa light chain and 65% lambda light chain for the detection of clonal proliferations associated with BNHL. Comparable diagnostic criteria for light chain ratios of 3:1 and 2:1 were similarly confirmed for cases of kappa clonal and lambda clonal proliferations, respectively. Neither the percent of B-cells present nor the ratio of T-helper cells to T-suppressor cells were of utility in the diagnosis of BNHL. These data confirm the numerical criteria for clonality previously obtained by cell counting studies of immunocytochemical preparations and characterize quantitative criteria for aid in the diagnosis of BNHL based on restricted surface light chain expression as measured by flow cytometry.