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Chapter 7

Abnormally high concentrations of κ and λ sFLCs may result from a number of clinical situations including immune stimulation, reduced renal clearance, or monoclonal plasma cell proliferative disorders [167]. Patients with either polyclonal hypergammaglobulinemia or renal impairment often have elevated κ and λ sFLCs due to increased synthesis (Chapter 35) or reduced renal clearance (Chapter 26), respectively. For patients with renal impairment, use of a renal reference interval for the κ/λ sFLC ratio may reduce the number of false-positive results (Section 6.3).

A significantly abnormal κ/λ sFLC ratio would only be expected to be due to a plasmaproliferative or lymphoproliferative disorder that secretes monoclonal FLCs and disturbs the normal balance between κ and λ secretion. Use of likelihood ratios when interpreting κ/λ sFLC ratios may improve clinical interpretation of sFLC results for the diagnosis of malignant plasma cell disorders [170].