Test Id : DMOGA

This test includes total protein, serum protein electrophoresis, heavy and light chain typing (kappa and lambda), and quantitation of kappa and lambda free light chains.

If a light chain is identified without a corresponding heavy chain during initial testing, immunofixation with IgD and IgE antisera will be performed at an additional charge.

For more information see:

-Multiple Myeloma: Laboratory Screening

-Amyloidosis: Laboratory Approach to Diagnosis

To monitor a patient with an established diagnosis of a monoclonal gammopathy, order TMOGA / Monoclonal Gammopathy, Monitoring, Serum.

Patient Preparation: Fasting (12 hour) preferred but not required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container /Tube: Plastic vial

Specimen Volume: 2 mL

Collection Instructions: Centrifuge and aliquot into a plastic vial.

• Amyloidosis: Laboratory Approach to Diagnosis
• Multiple Myeloma: Laboratory Screening

1.5 mL

Screening and diagnosing monoclonal gammopathies including analysis of free light chains

Assessing the risk of progression from monoclonal gammopathy of undetermined significance to multiple myeloma

This test includes total protein, serum protein electrophoresis, heavy and light chain typing (kappa and lambda), and quantitation of kappa and lambda free light chains.

If a light chain is identified without a corresponding heavy chain during initial testing, immunofixation with IgD and IgE antisera will be performed at an additional charge.

For more information see:

-Multiple Myeloma: Laboratory Screening

-Amyloidosis: Laboratory Approach to Diagnosis

Monoclonal proteins are markers of plasma cell proliferative disorders. The International Myeloma Working Group guidelines state that to adequately screen for a monoclonal protein, serum protein electrophoresis (SPE), immunofixation electrophoresis, and a serum free light chain (FLC) analysis should all be used. If amyloidosis is suspected, a 24-hour monoclonal protein studies should be performed.

The detection of M-proteins by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) has shown to be more analytically and clinically sensitive than immunofixation. In addition, the MALDI-TOF method can detect glycosylated light chains that have been demonstrated to be a risk factor for amyloidosis.

This expanded monoclonal protein testing panel provides the highest diagnostic sensitivity for the monoclonal light chain diseases such as primary amyloidosis and light chain deposition disease; disorders that often do not have serum monoclonal proteins in high enough concentration to be detected and quantitated by SPE. The FLC assay is specific for free kappa and lambda light chains and does not recognize light chains bound to intact immunoglobulin.

Monoclonal gammopathies may be present in a wide spectrum of diseases that include malignancies of plasma cells or B lymphocytes (multiple myeloma [MM], macroglobulinemia, plasmacytoma, B-cell lymphoma), disorders of monoclonal protein structure (primary amyloid, light chain deposition disease, cryoglobulinemia), and apparently benign, premalignant conditions (monoclonal gammopathy of undetermined significance [MGUS], smoldering MM). While the identification of the monoclonal gammopathy is a laboratory diagnosis, the specific clinical diagnosis is dependent on a number of other laboratory and clinical assessments.

If a monoclonal protein pattern is detected by MALDI-TOF MS, immunofixation electrophoresis, or FLC, a diagnosis of a monoclonal gammopathy is established. Once a monoclonal gammopathy has been diagnosed, the size of the clonal abnormality can be monitored by SPE or FLC and, in some instances, by quantitative immunoglobulins. In addition, if the patient is asymptomatic and has a diagnosis of MGUS, the monoclonal gammopathy screen provides the information (size of M-spike, monoclonal protein isotype, FLC kappa/lambda ratio) needed for a MGUS progression risk assessment (see Interpretation).

TOTAL PROTEIN:

> or =1 year: 6.3-7.9 g/dL

Reference values have not been established for patients that are younger than 12 months of age.

PROTEIN ELECTROPHORESIS

Albumin: 3.4-4.7 g/dL

Alpha-1-globulin: 0.1-0.3 g/dL

Alpha-2-globulin: 0.6-1.0 g/dL

Beta-globulin: 0.7-1.2 g/dL

Gamma-globulin: 0.6-1.6 g/dL

An interpretive comment is provided with the report.

Reference values have not been established for patients that are younger than 16 years of age.

M-PROTEIN ISOTYPE MALDI-TOF MS

No monoclonal protein detected

M-protein Isotype MALDI-TOF MS Flag

Negative

KAPPA-FREE LIGHT CHAIN

0.33-1.94 mg/dL

LAMBDA-FREE LIGHT CHAIN

0.57-2.63 mg/dL

KAPPA/LAMBDA-FREE LIGHT-CHAIN RATIO

0.26-1.65

Monoclonal Gammopathies:

-A characteristic monoclonal band (M-spike) is often found on serum protein electrophoresis (SPE) in the gamma globulin region and, more rarely, in the beta or alpha-2 regions. The finding of an M-spike, restricted migration, or hypogammaglobulinemic SPE pattern is suggestive of a possible monoclonal protein. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is performed to identify any immunoglobulin heavy and light chains present.

-A monoclonal IgG or IgA of greater than 3 g/dL is consistent with multiple myeloma (MM).

-A monoclonal IgG or IgA of less than 3 g/dL may be consistent with monoclonal gammopathy of undetermined significance (MGUS), primary systemic amyloidosis, early or treated myeloma, as well as a number of other monoclonal gammopathies.

-A monoclonal IgM of greater than 3 g/dL is consistent with macroglobulinemia.

-An abnormal serum free light chain (FLC) kappa/lambda (K/L) ratio in the presence of a normal MALDI-TOF MS suggests a monoclonal light chain process and should be followed by MPU / Monoclonal Protein Studies, 24 Hour, Urine.

-The initial identification of a serum M-spike greater than 1.5 g/dL on SPE should be followed by MPU / Monoclonal Protein Studies, 24 Hour, Urine.

-The initial identification of an IgM, IgA, or IgG M-spike greater than 4 g/dL, greater than 5 g/dL, and greater than 6 g/dL, respectively, a SVISC / Viscosity, Serum should be tested to rule out hyperviscosity syndrome.

After the initial identification of a monoclonal band, quantitation of the M-spike on follow-up SPE can be used to monitor the monoclonal gammopathy. However, if the monoclonal protein falls within the beta region (most commonly an IgA or an IgM) quantitative immunoglobulin levels may be a more useful tool to follow the monoclonal protein level than SPE. A decrease or increase of the M-spike that is greater than 0.5 g/dL is considered a significant change.

Patients with monoclonal light chain diseases who have no serum or urine M-spike may be monitored with the serum FLC value.

Patients suspected of having a monoclonal gammopathy may have normal serum SPE patterns. Approximately 11% of patients with MM have a completely normal serum SPE, with the monoclonal protein only identified by MALDI-TOF MS. Approximately 8% of MM patients have hypogammaglobulinemia without a quantifiable M-spike on SPE but identified by MALDI-TOF MS or FLC. Accordingly, a normal serum SPE does not rule out the disease, and SPE alone should not be used to screen for the disorder if the clinical suspicion is high.

MGUS Prognosis:

-Low-risk MGUS patients are defined as having an M-spike of less than 1.5 g/dL, IgG monoclonal protein, and a normal FLC K/L ratio (0.25-1.65), and these patients have a lifetime risk of progression to MM of less than 5%.

-High-risk MGUS patients (M-spike >1.5, IgA or IgM, abnormal FLC ratio) have a lifetime risk of progression to MM of 60%.

Other Abnormal SPE Findings:

-A qualitatively normal but elevated gamma fraction (polyclonal hypergammaglobulinemia) is consistent with infection, liver disease, or autoimmune disease.

-A depressed gamma fraction (hypogammaglobulinemia) is consistent with immune deficiency and can also be associated with primary amyloidosis or nephrotic syndrome.

-A decreased albumin (<2 g/dL), increased alpha-2 fraction (>1.1 g/dL), and decreased gamma fraction (<1 g/dL) is consistent with nephrotic syndrome and, when seen in an adult older than 40 years, should be followed by MPU / Monoclonal Protein Studies, 24 Hour, Urine.

-In the hereditary deficiency of a protein (eg, agammaglobulinemia, alpha-1-antitrypsin [A1AT] deficiency, hypoalbuminemia), the affected fraction is faint or absent.

-An absent alpha-1 fraction is consistent with A1AT deficiency disease and should be followed by a quantitative A1AT assay (AAT / Alpha-1-Antitrypsin, Serum).

Serum protein electrophoresis (SPE) alone is not considered an adequate screen for monoclonal gammopathies.

Very large IgG M-spikes (>4 g/dL) may saturate the protein stain. In these situations, quantitative IgG assays more accurately determine M-spike concentrations for monitoring disease progression or response to therapy.

Although the SPE M-spike is the recommended method of monitoring monoclonal gammopathies, IgA and IgM proteins contained in the beta fraction may be more accurately monitored by quantitative immunoglobulins.

Fibrinogen will migrate as a distinct band in the beta-gamma fraction but will be negative on immunofixation electrophoresis.

Hemolysis may augment the beta fraction.

Penicillin may split the albumin band.

Radiographic agents may produce an uninterpretable pattern.

1. 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;106:812-817

2. 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

3. Mills JR, Kohlhagen MC, Dasari S, et al: Comprehensive assessment of M-proteins using nanobody enrichment coupled to MALDI-TOF mass spectrometry. Clin Chem. 2016;62(10):1334-1344

4. Milani P, Murray DL, Barnidge DR, et al: The utility of MASS-FIX to detect and monitor monoclonal proteins in the clinic. Am J Hematol. 2017;92(8):772-779. doi: 10.1002/ajh.24772

Total Protein:

Divalent copper reacts in alkaline solution with protein peptide bonds to form the characteristic purple-colored biuret complex. Sodium potassium tartrate prevents the precipitation of copper hydroxide and potassium iodide prevents auto-reduction of copper. The color intensity is directly proportional to the protein concentration which can be determined photometrically.(Package insert: TP2 cobas. Roche Diagnostics; V 12.0, 11/2019)

Electrophoresis:

Serum proteins are separated in an electric field according to their size, shape, and electric charge. The separation is performed on agarose gels. The proteins are visualized by staining with acid blue and the intensity of staining is quantitated by densitometry. Multiplying by the serum total protein converts the percentage of protein in each fraction into serum concentration.(Instruction manual: Helena SPIFE Touch. Helena Laboratories, Corp; 11/2016; package insert: Helena SPIFE Touch SPE Pro 277. Helena Laboratories, Corp; 06/2018)

M-protein isotype:

M-protein isotype by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is performed with immunoaffinity purification followed by MALDI-TOF MS analysis. For the immunoaffinity purification, patient serum is applied to 5 separate immunoaffinity resins (CaptureSelect, Life Sciences) specific to immunoglobulin G, A, M, K, and L. Unbound protein is washed away and the isolated immunoglobulins are broken down in to their reduced to separate the heavy and light chains subunits to be analyzed via MALDI-TOF mass spectrometry. The 5 separate spectra from each patient immunopurification are overlaid and investigated for the overabundance of an immunoglobulin and/or immunoglobulin light chain.(Kohlhagen M, Dasari S, Willrich M, et al: Automation and validation of a MALDI-TOF MS (Mass-Fix) replacement of immunofixation electrophoresis in the clinical lab. Clin Chem Lab Med. 2020 Aug 3;59(1):155-163. doi: 10.1515/cclm-2020-0581)

Free Light Chains:

The determination of the soluble antigen concentration by turbidimetric methods involves the reaction with specific antiserum to form insoluble complexes. When light is passed through the suspension formed a portion of the light is transmitted and focused onto a photodiode by an optical lens system. The amount of transmitted light is indirectly proportional to the specific protein concentration in the test sample. Concentrations are automatically calculated by reference to a calibrations curve stored within the instrument.(Package inserts: Optilite Freelite Kappa Free Kit. The Binding Site Group, Ltd; 06/2015; Optilite Freelite Lambda Free Kit. The Binding Site Group, Ltd; 06/2015)

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This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

83521 x 2

84155

84165

0077U

86334 (if appropriate)