Traditional Methods
Laboratory Procedures
Serum protein electrophoresis in nine patients with Light Chain Multiple Myeloma and one normal sample together with the concentrations of free light chains (mg/L) measured by Freelite.
Current laboratory protocols for multiple myeloma diagnosis are generally based on the detection of whole immunoglobulin monoclonal protein (M-protein) in serum by serum protein electrophoresis (SPE). This is followed by immunofixation electrophoresis (IFE) to confirm monoclonality and class of the M-protein. As 15% of all cases of Multiple Myeloma are Light Chain (Bence Jones) Multiple Myeloma with little or no detectable protein in the serum, further analysis is required. A 24-hour urine sample is concentrated x100 then analysed for the presence of Bence Jones protein by electrophoresis. Quantification may be performed by densitometric scanning of the gel.
The SPE assay shown illustrates the difficulties detecting M-protein bands in some samples by this technique. All samples have detectable levels (and in some cases high levels) of free light chains by Freelite.
Limitations of Current Practice
Serial free light chain measurements in serum samples from a Bence Jones lambda myeloma patient undergoing treatment, compared with urine densitometric scan levels1.
- Detection of paraproteins in urine may occur late in disease
- Patient compliance with 24 hour urine collections
- Sample variability
- Transport and storage of large volumes of urine and the associated costs
- Labour intensive process
- Sensitivity of current methods
- Semi-quantitative measurement only
- Imprecision of densitometric scanning can make monitoring difficult
Problems of current assays for free light chain detection in serum revolve around the lack of sensitivity of SPE and IFE, and issues with urine assays2.
A fully automated and precise result on serum is obviously preferable but has not, until the availability of Freelite assays, been achievable.
Review the evidence for an initial investigation protocol using Freelite.
References
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Carr-Smith et al.
The effect on laboratory organisation of introducing serum free light chain assays.
Clinical Chemistry 2004;50:6 P.A.76
