From the Guidelines
The simplest test to screen for Bence Jones (immunoglobulin light chain) protein in the urine is urine protein electrophoresis, as stated in the 2019 consensus report by the international kidney and monoclonal gammopathy research group 1. When screening for Bence Jones protein, it is essential to use a validated assay, and according to the 2019 report, urinary light-chain assays have not been validated and should not be used to quantify the amount of light chain in a 24-hour urine specimen. In contrast, serum analysis can be done using serum free light chain (FLC) assay, which has been shown to be useful in screening for multiple myeloma and related plasma cell disorders, as stated in the 2017 NCCN clinical practice guidelines in oncology 1. However, it is crucial to note that the serum FLC assay cannot replace the 24-hour urine protein electrophoresis for monitoring patients with measurable urinary M-proteins. Some key points to consider when screening for Bence Jones protein include:
- Using a validated assay, such as urine protein electrophoresis or serum FLC assay
- Considering the type of assay used, as different assays may have different performance characteristics and may be affected by renal impairment to varying degrees
- Using the same assay to monitor a particular patient throughout their treatment to ensure accurate relative quantification
- Consulting with a healthcare provider to recommend appropriate testing based on the specific clinical situation and symptoms.
From the Research
Screening for Bence Jones Protein
- The simplest test to screen for Bence Jones (immunoglobulin light chain) protein in the urine or serum is serum free light chain analysis 2, 3, 4.
- Serum free light chain analysis has been shown to be highly sensitive for detecting Bence Jones proteinuria, with a sensitivity of 98% 3.
- This test can be used as an alternative to urine protein electrophoresis (UPE) for screening for monoclonal gammopathies 3, 4.
- The use of serum free light chain analysis can facilitate earlier diagnosis and treatment of patients with monoclonal gammopathies, particularly those with light-chain multiple myeloma 2, 3.
Comparison with Urine Tests
- Urine protein electrophoresis and urine immunofixation electrophoresis (IFE) are also used to detect Bence Jones proteinuria, but serum free light chain analysis has been shown to be more sensitive and convenient 2, 5, 3.
- Serum free light chain analysis can detect Bence Jones proteinuria even when urine tests are negative, and can provide a more accurate diagnosis 2, 3.
- However, urine IFE can detect free light chains in urine samples even at low concentrations and offers higher sensitivity compared to serum electrophoresis and serum IFE 5.
Clinical Implications
- The use of serum free light chain analysis as a screening test for Bence Jones proteinuria can improve the detection and diagnosis of monoclonal gammopathies 3, 4.
- This test can be used in conjunction with serum protein electrophoresis (SPEP) to identify additional patients with monoclonal gammopathies 4.
- The cost and quality implications of routinely measuring serum free light chains have been shown to be offset by the benefits of improved diagnosis and treatment 4.