From the Guidelines
Serum immunofixation for proteinuria should be checked to detect and quantify monoclonal proteins, which is crucial for the diagnosis and management of multiple myeloma (MM) with potential kidney damage, as recommended by the most recent guidelines 1. The diagnostic approach for suspected MM with proteinuria and kidney damage involves several essential tests, including:
- Serum and urine protein electrophoresis
- Immunofixation
- Serum free light chain assay
- Complete blood count
- Comprehensive metabolic panel with calcium
- Creatinine clearance
- 24-hour urine protein
- Bone marrow biopsy
- Skeletal imaging (preferably low-dose whole-body CT) These tests help detect and quantify monoclonal proteins, assess kidney function, and evaluate bone marrow plasma cell infiltration and lytic bone lesions. Kidney damage in MM is often due to cast nephropathy from excess light chains, requiring prompt intervention. Treatment should be initiated immediately upon diagnosis to prevent irreversible kidney damage, and may include a triplet regimen of bortezomib, cyclophosphamide, and dexamethasone, as well as supportive measures such as adequate hydration, avoidance of nephrotoxic medications, and bisphosphonates for hypercalcemia, as recommended by the guidelines 1. The serum free light chain assay is a valuable tool for monitoring disease response and progression, particularly in patients with non-secretory myeloma, and is included in the initial diagnostic workup for MM 1. Early nephrology consultation is recommended for collaborative management of these complex patients, and kidney function should be monitored closely during treatment, as improvement often occurs within 2-3 cycles of effective therapy.
From the FDA Drug Label
Complete response (CR) required <5% plasma cells in the marrow, 100% reduction in M-protein, and a negative immunofixation test (IF-). Partial response (PR) requires ≥50% reduction in serum myeloma protein and ≥90% reduction of urine myeloma protein on at least two occasions for a minimum of at least six weeks along with stable bone disease and normal calcium Near complete response (nCR) was defined as meeting all the criteria for complete response including 100% reduction in M-protein by protein electrophoresis, however M-protein was still detectable by immunofixation (IF+)
The diagnostic and treatment approach for suspected multiple myeloma (MM) with proteinuria and potential kidney damage involves checking serum immunofixation for proteinuria to assess the level of M-protein in the blood and urine. This is crucial in determining the response to treatment, such as bortezomib, and in monitoring the progression of the disease. Key points to consider include:
- Complete response (CR): 100% reduction in M-protein and a negative immunofixation test (IF-)
- Partial response (PR): ≥50% reduction in serum myeloma protein and ≥90% reduction of urine myeloma protein
- Near complete response (nCR): meets all criteria for CR, but M-protein is still detectable by immunofixation (IF+) 2
From the Research
Diagnostic Approach for Suspected Multiple Myeloma (MM) with Proteinuria
- Serum immunofixation is checked for proteinuria to identify and characterize the monoclonal component in multiple myeloma and related disorders 3.
- The presence of Bence-Jones (BJ) proteinuria is significantly associated with renal failure in multiple myeloma patients 3.
- Immunofixation electrophoresis is a helpful tool in detecting the M-protein, which is a defining feature of monoclonal gammopathies 4.
Laboratory Tests for Monoclonal Gammopathies
- Protein electrophoresis, immunofixation, immunoglobulin quantitation, serum free light chains, and heavy-light chain assays are employed to detect M-proteins 4.
- Mass spectrometry-based methods, such as miRAMM, can detect the presence of M-proteins with superior sensitivity compared to gel-based techniques 5.
- Serum protein electrophoresis is used to identify patients with multiple myeloma and other serum protein disorders, and can help differentiate multiple myeloma from other causes of monoclonal gammopathy 6.
Role of Serum Protein Electrophoresis in Detecting Multiple Myeloma
- Serum protein electrophoresis is an easy-to-perform laboratory test that can be used for detection and quantification of monoclonal gammopathy 7.
- It is recommended as a preliminary test for suspected cases of multiple myeloma, and can help differentiate monoclonal gammopathy of undetermined significance (MGUS) from multiple myeloma 7.
- The detection of M-protein in serum and urine electrophoresis is crucial in diagnosing multiple myeloma, and correlation with bone marrow biopsy and clinical profile is necessary for accurate diagnosis 7.