Clinical Review & Education
JAMA Diagnostic Test Interpretation
Protein Electrophoresis and Immunofixation for the Diagnosis of Monoclonal Gammopathies S. Vincent Rajkumar, MD; Robert A. Kyle, MD
A woman in her 70s presented with numbness in her hands that had progressively worsened over the last 6 months.. She did not have diabetes mellitus and she did not drink alcohol. On physical examination, she had no pallor, lymphadenopathy, or organomegaly. She had evidence of bilateral carpal tunnel syndrome (positive Phalen test and Tinel sign bilaterally) and reduced deep tendon reflexes in the upper and lower extremities bilaterally. Laboratory test results for complete blood cell count, serum calcium, serum creatinine, blood glucose, serum thyroid-stimulating hormone, and serum B12 were within normal limits. Because of unexplained neuropathy, a workup to detect an underlying monoclonal gammopathy was done, including serum protein electrophoresis, immunofixation, and free light chain assay (see Table).
HOW DO YOU INTERPRET THESE TEST RESULTS?
A. The patient most likely has multiple myeloma. B. The patient most likely has monoclonal gammopathy of undetermined significance (MGUS).
Table. Patient’s Laboratory Values Laboratory Test
Value
Reference Range
Serum protein electrophoresis Total protein, g/dL
6.6
6.3-7.9
Albumin, g/dL
3.2
3.4-4.7
α1-globulin, g/dL
0.3
0.1-0.3
α2-globulin, g/dL
1.1
0.6-1.0
β-globulin, g/dL
0.9
0.7-1.2
γ-globulin, g/dL
1.1
Monoclonal protein, g/dL Serum protein immunofixation
C. The patient most likely has Waldenström macroglobulinemia. D. This patient most likely has light chain monoclonal gammopathy.
0.6-1.6
Present, 0.6
Absent, 0
Monoclonal IgG κ
Absent
Serum free light chain assay Serum free κ-light chain, mg/dL
0.994
0.33-1.94
Serum free λ-light chain, mg/dL
0.549
0.57-2.63
Serum κ/λ light-chain ratio
1.81
0.26-1.65
Answer B. This patient most likely has a monoclonal gammopathy of undetermined significance (MGUS).
Test Characteristics Clonal plasma cell disorders are characterized by the presence of monoclonal proteins in serum, urine, or both. Monoclonal proteins are immunoglobulins (or immunoglobulin fragments) secreted by a proliferating plasma cell clone. Patients suspected to have a clonal plasma cell disorder should be screened for the presence of a Quiz at jama.com monoclonal protein using serum protein electrophoresis, serum immunofixation, and the free light chain (FLC) assay.1 Serum protein electrophoresis separates proteins in an electric field, according to their size and electrical charge, and is used to determine the presence or absence of a monoclonal protein and to estimate its concentration. Serum immunofixation allows detection of small monoclonal proteins, and is used to further characterize the monoclonal protein by determining the type of immunoglobulin heavy-chain class (IgG, IgA, IgM, IgD, or IgE) and light-chain type (κ or λ). 2160
Clonal plasma cell proliferation is also often associated with excess secretion of free immunoglobulin light chains, and in some cases only FLCs are secreted without any heavy-chain expression. The serum FLC assay is required to detect FLCs that can be otherwise missed on electrophoresis and immunofixation. The normal κ to λ FLC ratio is disrupted in the presence of clonal proliferation. An abnormal FLC ratio also has prognostic value in predicting risk of progression in MGUS and related disorders.2 The Medicare reimbursement for serum protein electrophoresis is$20,serumimmunofixation$31,andserumfreelightchainassay$37.
Application of Test Results to This Patient Screening for an underlying monoclonal protein is indicated in patients with unexplained neuropathy because MGUS is a potentially treatable etiologic factor. This patient has a small monoclonal protein, measuring 0.6 g/dL. Serum immunofixation identifies this monoclonal protein as IgG κ subtype. The serum FLC ratio is abnormal (1.81). A monoclonal protein indicates the presence of a premalignant plasma cell disorder, such as MGUS or smoldering multiple myeloma; or a malignancy, such as multiple myeloma, solitary plasmacytoma, or Waldenström macroglobulinemia. MGUS is the precursor of multiple
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JAMA Diagnostic Test Interpretation Clinical Review & Education
Box. Key Points of Monoclonal Gammopathy of Undetermined Significance (MGUS) • MGUS is characterized by the presence of a monoclonal protein on serum protein electrophoresis and immunofixation. • MGUS does not require therapy, but most patients should be followed on a regular basis. • MGUS is an asymptomatic, premalignant plasma cell proliferative disorder.
myeloma and related plasma cell malignancies.3 The relatively small size of the monoclonal protein, and the absence of anemia, hypercalcemia, or renal failure favor a diagnosis of MGUS rather than multiple myeloma. However, a bone marrow biopsy is often needed to differentiate MGUS, smoldering multiple myeloma, and multiple myeloma.4 Waldenström macroglobulinemia is associated with an IgM type of monoclonal protein. Light-chain MGUS is characterized by absence of heavy-chain expression on immunofixation; the monoclonal protein in this patient is an intact immunoglobulin with both heavy- (IgG) and light-chain (κ) expression. Other disorders associated with a monoclonal protein include immunoglobulin lightchain amyloidosis, monoclonal immunoglobulin deposition disease, cryoglobulinemia, peripheral neuropathy, membranoproliferative glomerulonephritis, and osteoporosis (see Box).4,5
What Are Alternative Diagnostic Approaches? A 24-hour urine protein electrophoresis and immunofixation can be used in place of the serum FLC assay, but are more cumbersome. ARTICLE INFORMATION Author Affiliations: Division of Hematology, Mayo Clinic, Rochester, Minnesota. Corresponding Author: Robert A. Kyle, MD, Division of Hematology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 ([email protected]). Section Editor: Mary McGrae McDermott, MD, Senior Editor. Conflict of Interest Disclosures: None reported. REFERENCES 1. Katzmann JA, Dispenzieri A, Kyle RA, et al. Elimination of the need for urine studies in the screening algorithm for monoclonal gammopathies by using serum immunofixation and free light chain assays. Mayo Clin Proc. 2006;81(12):1575-1578.
A bone marrow biopsy is usually recommended for patients suspected to have MGUS with a monoclonal protein of at least 1.5 g/dL, non-IgG type, abnormal serum FLC ratio, or any other concern for underlying myeloma or amyloidosis.6
Patient Outcome Bone marrow biopsy was deferred. The patient was treated with 10 mg of triamcinolone acetonide injected into the carpal tunnel on each side. There was no improvement and therefore surgical therapy is planned. The patient is also being followed up for MGUS annually. Therapy to eradicate the monoclonal protein would have caused adverse effects and is usually reserved for patients with more extensive progressive neuropathy.
Clinical Bottom Line • MGUS is present in approximately 2% to 3% of the white population older than 50 years.7,8 • Prevalence of MGUS is higher in black individuals and slightly lower in Hispanic individuals.8 • MGUS is associated with a risk of progression to multiple myeloma or related disorder at a rate of 1% per year.3,9 The risk of progression is influenced by the concentration and type of the monoclonal protein and the serum FLC ratio.10 • Most patients with MGUS should be evaluated with a medical history, and physical examination, complete blood cell count, calcium and creatinine levels, and serum electrophoresis in 6 months, and annually thereafter.6 • Treatment is not indicated for MGUS (see Box).
2. Dispenzieri A, Kyle R, Merlini G, et al. International Myeloma Working Group guidelines for serum-free light chain analysis in multiple myeloma and related disorders. Leukemia. 2009;23 (2):215-224. 3. Kyle RA, Therneau TM, Rajkumar SV, et al. A long-term study of prognosis in monoclonal gammopathy of undetermined significance. N Engl J Med. 2002;346(8):564-569. 4. Kyle RA, Rajkumar SV. Criteria for diagnosis, staging, risk stratification and response assessment of multiple myeloma. Leukemia. 2009;23(1):3-9. 5. Bladé J. Clinical practice: monoclonal gammopathy of undetermined significance. N Engl J Med. 2006;355(26):2765-2770. 6. Kyle RA, Durie BGM, Rajkumar SV, et al. Monoclonal gammopathy of undetermined significance (MGUS) and smoldering (asymptomatic) multiple myeloma. Leukemia. 2010;24(6):1121-1127.
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7. Kyle RA, Therneau TM, Rajkumar SV, et al. Prevalence of monoclonal gammopathy of undetermined significance. N Engl J Med. 2006; 354(13):1362-1369. 8. Landgren O, Graubard BI, Katzmann JA, et al. Racial disparities in the prevalence of monoclonal gammopathies. Leukemia. 2014;28(7):1537-1542. 9. Turesson I, Kovalchik SA, Pfeiffer RM, et al. Monoclonal gammopathy of undetermined significance and risk of lymphoid and myeloid malignancies. Blood. 2014;123(3):338-345. 10. Rajkumar SV, Kyle RA, Therneau TM, et al. Serum free light chain ratio is an independent risk factor for progression in monoclonal gammopathy of undetermined significance. Blood. 2005;106(3): 812-817.
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JAMA Diagnostic Test Interpretation
Protein Electrophoresis and Immunofixation for the Diagnosis of Monoclonal Gammopathies S. Vincent Rajkumar, MD; Robert A. Kyle, MD
A woman in her 70s presented with numbness in her hands that had progressively worsened over the last 6 months.. She did not have diabetes mellitus and she did not drink alcohol. On physical examination, she had no pallor, lymphadenopathy, or organomegaly. She had evidence of bilateral carpal tunnel syndrome (positive Phalen test and Tinel sign bilaterally) and reduced deep tendon reflexes in the upper and lower extremities bilaterally. Laboratory test results for complete blood cell count, serum calcium, serum creatinine, blood glucose, serum thyroid-stimulating hormone, and serum B12 were within normal limits. Because of unexplained neuropathy, a workup to detect an underlying monoclonal gammopathy was done, including serum protein electrophoresis, immunofixation, and free light chain assay (see Table).
HOW DO YOU INTERPRET THESE TEST RESULTS?
A. The patient most likely has multiple myeloma. B. The patient most likely has monoclonal gammopathy of undetermined significance (MGUS).
Table. Patient’s Laboratory Values Laboratory Test
Value
Reference Range
Serum protein electrophoresis Total protein, g/dL
6.6
6.3-7.9
Albumin, g/dL
3.2
3.4-4.7
α1-globulin, g/dL
0.3
0.1-0.3
α2-globulin, g/dL
1.1
0.6-1.0
β-globulin, g/dL
0.9
0.7-1.2
γ-globulin, g/dL
1.1
Monoclonal protein, g/dL Serum protein immunofixation
C. The patient most likely has Waldenström macroglobulinemia. D. This patient most likely has light chain monoclonal gammopathy.
0.6-1.6
Present, 0.6
Absent, 0
Monoclonal IgG κ
Absent
Serum free light chain assay Serum free κ-light chain, mg/dL
0.994
0.33-1.94
Serum free λ-light chain, mg/dL
0.549
0.57-2.63
Serum κ/λ light-chain ratio
1.81
0.26-1.65
Answer B. This patient most likely has a monoclonal gammopathy of undetermined significance (MGUS).
Test Characteristics Clonal plasma cell disorders are characterized by the presence of monoclonal proteins in serum, urine, or both. Monoclonal proteins are immunoglobulins (or immunoglobulin fragments) secreted by a proliferating plasma cell clone. Patients suspected to have a clonal plasma cell disorder should be screened for the presence of a Quiz at jama.com monoclonal protein using serum protein electrophoresis, serum immunofixation, and the free light chain (FLC) assay.1 Serum protein electrophoresis separates proteins in an electric field, according to their size and electrical charge, and is used to determine the presence or absence of a monoclonal protein and to estimate its concentration. Serum immunofixation allows detection of small monoclonal proteins, and is used to further characterize the monoclonal protein by determining the type of immunoglobulin heavy-chain class (IgG, IgA, IgM, IgD, or IgE) and light-chain type (κ or λ). 2160
Clonal plasma cell proliferation is also often associated with excess secretion of free immunoglobulin light chains, and in some cases only FLCs are secreted without any heavy-chain expression. The serum FLC assay is required to detect FLCs that can be otherwise missed on electrophoresis and immunofixation. The normal κ to λ FLC ratio is disrupted in the presence of clonal proliferation. An abnormal FLC ratio also has prognostic value in predicting risk of progression in MGUS and related disorders.2 The Medicare reimbursement for serum protein electrophoresis is$20,serumimmunofixation$31,andserumfreelightchainassay$37.
Application of Test Results to This Patient Screening for an underlying monoclonal protein is indicated in patients with unexplained neuropathy because MGUS is a potentially treatable etiologic factor. This patient has a small monoclonal protein, measuring 0.6 g/dL. Serum immunofixation identifies this monoclonal protein as IgG κ subtype. The serum FLC ratio is abnormal (1.81). A monoclonal protein indicates the presence of a premalignant plasma cell disorder, such as MGUS or smoldering multiple myeloma; or a malignancy, such as multiple myeloma, solitary plasmacytoma, or Waldenström macroglobulinemia. MGUS is the precursor of multiple
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Copyright 2014 American Medical Association. All rights reserved.
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JAMA Diagnostic Test Interpretation Clinical Review & Education
Box. Key Points of Monoclonal Gammopathy of Undetermined Significance (MGUS) • MGUS is characterized by the presence of a monoclonal protein on serum protein electrophoresis and immunofixation. • MGUS does not require therapy, but most patients should be followed on a regular basis. • MGUS is an asymptomatic, premalignant plasma cell proliferative disorder.
myeloma and related plasma cell malignancies.3 The relatively small size of the monoclonal protein, and the absence of anemia, hypercalcemia, or renal failure favor a diagnosis of MGUS rather than multiple myeloma. However, a bone marrow biopsy is often needed to differentiate MGUS, smoldering multiple myeloma, and multiple myeloma.4 Waldenström macroglobulinemia is associated with an IgM type of monoclonal protein. Light-chain MGUS is characterized by absence of heavy-chain expression on immunofixation; the monoclonal protein in this patient is an intact immunoglobulin with both heavy- (IgG) and light-chain (κ) expression. Other disorders associated with a monoclonal protein include immunoglobulin lightchain amyloidosis, monoclonal immunoglobulin deposition disease, cryoglobulinemia, peripheral neuropathy, membranoproliferative glomerulonephritis, and osteoporosis (see Box).4,5
What Are Alternative Diagnostic Approaches? A 24-hour urine protein electrophoresis and immunofixation can be used in place of the serum FLC assay, but are more cumbersome. ARTICLE INFORMATION Author Affiliations: Division of Hematology, Mayo Clinic, Rochester, Minnesota. Corresponding Author: Robert A. Kyle, MD, Division of Hematology, Mayo Clinic, 200 First St SW, Rochester, MN 55905 ([email protected]). Section Editor: Mary McGrae McDermott, MD, Senior Editor. Conflict of Interest Disclosures: None reported. REFERENCES 1. Katzmann JA, Dispenzieri A, Kyle RA, et al. Elimination of the need for urine studies in the screening algorithm for monoclonal gammopathies by using serum immunofixation and free light chain assays. Mayo Clin Proc. 2006;81(12):1575-1578.
A bone marrow biopsy is usually recommended for patients suspected to have MGUS with a monoclonal protein of at least 1.5 g/dL, non-IgG type, abnormal serum FLC ratio, or any other concern for underlying myeloma or amyloidosis.6
Patient Outcome Bone marrow biopsy was deferred. The patient was treated with 10 mg of triamcinolone acetonide injected into the carpal tunnel on each side. There was no improvement and therefore surgical therapy is planned. The patient is also being followed up for MGUS annually. Therapy to eradicate the monoclonal protein would have caused adverse effects and is usually reserved for patients with more extensive progressive neuropathy.
Clinical Bottom Line • MGUS is present in approximately 2% to 3% of the white population older than 50 years.7,8 • Prevalence of MGUS is higher in black individuals and slightly lower in Hispanic individuals.8 • MGUS is associated with a risk of progression to multiple myeloma or related disorder at a rate of 1% per year.3,9 The risk of progression is influenced by the concentration and type of the monoclonal protein and the serum FLC ratio.10 • Most patients with MGUS should be evaluated with a medical history, and physical examination, complete blood cell count, calcium and creatinine levels, and serum electrophoresis in 6 months, and annually thereafter.6 • Treatment is not indicated for MGUS (see Box).
2. Dispenzieri A, Kyle R, Merlini G, et al. International Myeloma Working Group guidelines for serum-free light chain analysis in multiple myeloma and related disorders. Leukemia. 2009;23 (2):215-224. 3. Kyle RA, Therneau TM, Rajkumar SV, et al. A long-term study of prognosis in monoclonal gammopathy of undetermined significance. N Engl J Med. 2002;346(8):564-569. 4. Kyle RA, Rajkumar SV. Criteria for diagnosis, staging, risk stratification and response assessment of multiple myeloma. Leukemia. 2009;23(1):3-9. 5. Bladé J. Clinical practice: monoclonal gammopathy of undetermined significance. N Engl J Med. 2006;355(26):2765-2770. 6. Kyle RA, Durie BGM, Rajkumar SV, et al. Monoclonal gammopathy of undetermined significance (MGUS) and smoldering (asymptomatic) multiple myeloma. Leukemia. 2010;24(6):1121-1127.
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7. Kyle RA, Therneau TM, Rajkumar SV, et al. Prevalence of monoclonal gammopathy of undetermined significance. N Engl J Med. 2006; 354(13):1362-1369. 8. Landgren O, Graubard BI, Katzmann JA, et al. Racial disparities in the prevalence of monoclonal gammopathies. Leukemia. 2014;28(7):1537-1542. 9. Turesson I, Kovalchik SA, Pfeiffer RM, et al. Monoclonal gammopathy of undetermined significance and risk of lymphoid and myeloid malignancies. Blood. 2014;123(3):338-345. 10. Rajkumar SV, Kyle RA, Therneau TM, et al. Serum free light chain ratio is an independent risk factor for progression in monoclonal gammopathy of undetermined significance. Blood. 2005;106(3): 812-817.
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