FIGURE 1.

Relationship between the κ and λ free light chain sum (Σ FLC) and the free light chain ratio (rFLC). Most study participants had both normal Σ FLC and rFLC (section v, 86.3%). By definition of light chain monoclonal gammopathy of undetermined significance,² no participant had both a high Σ FLC and an abnormal rFLC (low [section iii] or high [section ix]). The distribution of the remaining participants by section was as follows: i, 0.1%; ii, 0.4%; iv, 1.2%; vi, 11.2%; vii, 0.1%; and viii, 0.8%. Blue represents the reference range for Σ FLC (0.95-4.35 mg/dL), yellow represents the reference range for rFLC (0.26-1.65), and green represents those study participants in whom both the Σ FLC and rFLC were normal.