Sensitivity of Assays
Sensitivity of SPE and IFE
Problems of current assays for free light chain detection in serum revolve around the lack of sensitivity of SPE and IFE.
| Kappa | Lambda | |
|---|---|---|
| SPE | 500-2000 mg/L | 500-2000 mg/L |
| IFE | 150-500 mg/L | 150-500 mg/L |
| Freelite | 0.3 mg/L | 0.5 mg/L |
Due to the sensitivity of current serum methods, it is recommended to test a 24 hour urine sample for free light chains (Bence Jones protein). However, serum is a superior medium for numerous reasons.
This kappa/lambda plot shows the number of samples that would be misclassified as negative using SPE and IFE, but are detected with serum free light chain assays.
Since normal FLC concentrations are considerably below the detection limit of all the electrophoresis methods, some patients will always be missed by these techniques.
Freelite quantifies free light chains into the normal range, and is more sensitive than current diagnostic tests available for myeloma.
(pIgG - polyclonal hypergammaglobulinaemia) - Click to enlarge.
Monitoring Light Chain Multiple Myeloma Patients
This data illustrates the value of high sensitivity serum free light chain assays for monitoring patients with myeloma.
For these patients, urine free light chain concentrations were too low for reliable quantification. However, serum free light chains could be measured at all times.1
Alyanakian et al. concluded, "Immunonephelometric measurement of serum free light chains are a reliable method for follow up of patients with light chain secreting monoclonal gammopathies". Also that for cases featuring hardly measurable amounts of light chain in the urine "...the serum free light chain assay proved sensitive enough for correlation with clinical events."
Summary
- Freelite serum assays are more sensitive than conventional urine methods.
- Using the serum kappa/lambda ratio ensures confidence in results irrespective of possible renal impairment.
Go to Monitoring Treatment and Disease for further examples of high sensitivity Freelite assays for monitoring myeloma patients.
