As a first step, using six-color flow cytometry and a gating strategy that has been described previously,19 we identified prediagnostic B-cell clones in 42 of 45 patients (93%) on the basis of the presence of an abnormal kappa:lambda ratio (>3:1) or negativity for both chains (Fig. 1). The results for the remaining three patients (Patients 6, 27, and 30) were indeterminate, since there were too few cells in the sample to perform a reliable assessment of clonality (Table 2). Among the 42 patients with a detectable prediagnostic clone, the B cells showed a kappa restriction in 28 patients (67%), a lambda restriction in 8 (19%), and an apparent negativity for both light chains in 3 (7%). On the basis of flow cytometry, in three patients (Patients 19, 26, and 38) (7%), the B cells showed a biclonal pattern of light-chain restriction.
