[Clinical usefulness of serum free light chain measurement in monoclonal gammopathy].

Recently, a highly sensitive assay (FREELITE) capable of measuring serum immunoglobulin-free light chains (FLC) was developed. An abnormal kappa/lambda ratio supports the presence of clonal plasma cell expansion. Using this assay, we measured serum and urine samples of 178 healthy volunteers, 184 patients with polyclonal gamma-globulinemia and 150 patients with monoclonal gamma-globulinemia. The diagnostic sensitivity of the FLC assays for monoclonal gammopathies was 88.0% and the specificity for healthy volunteers and polyclonal gammopathies was 96.1%. The minimal detection sensitivity of this assay for serum FLC was 0.3 mg/l and was greater than 100-fold more sensitive than serum protein electrophoresis (SPE). The combination of FLC with SPE and immunoelectrophoresis identified 99% of patients with monoclonal gammopathies. Effective treatment often leads to a more rapid reduction of the involved FLC level relative to the intact immunoglobulin or total light chain concentration because the half-life of FLC is <6 hours. These observations suggest that FREELITE is useful for diagnosis, disease monitoring and assessment of response to treatment in patients with monoclonal gammopathies such as multiple myeloma and AL amyloidosis.

[Evaluation of the clinical relevance of serum measurements of free-light chains in patients with multiple myeloma].

Measurement of serum free-light chains (FLCs) was performed using a recently developed immunoassay in 180 healthy individuals, 16 patients with multiple myeloma, and each 1 patient with Waldenström's macroglobulinemia, primary amyloidosis, or MGUS (monoclonal gammopathy of undetermined significance) to evaluate the clinical relevance of FLCs in the diagnosis and disease monitoring. Serum FLC levels of each patient were elevated compared with the levels of healthy individuals. The changes in FLC levels after treatment and at the time of relapse occurred earlier than those in serum immunoglobulin levels due to the short half-life of FLCs. Serum FLC levels were elevated in patients with Bence Jones type myeloma in spite of negative urinary immunoelectrophoresis. The serum FLC assay is a sensitive and useful tool for the diagnosis and monitoring of multiple myeloma and other B-cell proliferative disorders.