Immunofixation Electrophoresis in Multiple Myeloma
Immunofixation electrophoresis (IFE) is essential for both initial diagnosis and monitoring of multiple myeloma, as it identifies the specific type of monoclonal protein (M-protein) and is required to confirm complete response to treatment. 1
Role in Initial Diagnosis
IFE must be performed on both serum and urine as part of the initial diagnostic workup for all suspected multiple myeloma patients. 1
Serum Immunofixation Electrophoresis (SIFE)
- Provides specific identification of the M-protein type by characterizing the heavy chain (IgG, IgA, or IgM) and light chain (kappa or lambda) components 1
- Detects M-proteins that may be missed by serum protein electrophoresis (SPEP) alone, particularly in patients with low-level or atypical M-proteins 2, 3
- Should be combined with SPEP and serum free light chain (FLC) assay to achieve high sensitivity for screening multiple myeloma and related plasma cell disorders 1
- Achieves 100% detection rate of monoclonal gammopathies compared to only 69.6% detection by SPEP alone 2, 3
Urine Immunofixation Electrophoresis (UIFE)
- Must be performed on a 24-hour urine collection to detect Bence Jones proteins (monoclonal free light chains) 1, 4
- Should be performed even when urine protein electrophoresis shows no measurable protein or visible peak, as immunofixation can still detect monoclonal proteins 4
- Random urine samples are insufficient and cannot replace 24-hour collection, even when corrected for creatinine 4
- Approximately 20% of multiple myeloma patients have secretory urinary M-proteins, while 3% have nonsecretory disease with neither serum nor urine M-protein 1
Role in Treatment Monitoring
IFE is required to document complete response and stringent complete response according to International Myeloma Working Group criteria. 1
Response Assessment
- Complete response requires negative immunofixation of both serum and urine 4
- The FLC ratio must also be normal to document stringent complete response 1
- Serial measurements using the same test method are essential to ensure accurate relative quantification and track disease progression 1
Monitoring During Novel Therapy
- Special HYDRASHIFT assays are required for patients receiving daratumumab or isatuximab (IgG-κ monoclonal antibodies) to avoid false-positive results caused by therapeutic antibody interference 5
- Standard IFE can misidentify therapeutic antibodies as residual M-protein, leading to inaccurate assessment of complete response 5
Critical Pitfalls to Avoid
Diagnostic Phase
- Never rely on SPEP alone without IFE, as approximately 30% of monoclonal gammopathies may be missed 2, 3
- Always perform IFE on concentrated 24-hour urine samples, not random specimens, to avoid false-negative results 4
- Ensure complete 24-hour urine collection, as incomplete collection leads to underestimation of urinary M-protein burden 4
Monitoring Phase
- Use the same testing method for serial studies to ensure accurate comparison of M-protein levels over time 1
- Do not substitute serum FLC assay for 24-hour urine protein electrophoresis in patients with measurable urinary M-proteins 1
- Implement HYDRASHIFT methodology when monitoring patients on daratumumab or isatuximab to prevent false-positive IFE results 5
Emerging Technologies
Mass spectrometry (EXENT&FLC-MS) demonstrates superior sensitivity compared to IFE, detecting M-protein in patients classified as IFE-negative and providing better prognostic discrimination after consolidation therapy 6, 7. However, IFE remains the current standard method recommended by NCCN guidelines for routine clinical practice 1.