From the Guidelines
Screening for Monoclonal Gammopathy of Undetermined Significance (MGUS) requires both serum and urine tests to detect abnormal protein production by plasma cells. The essential blood tests include:
- Serum protein electrophoresis (SPEP), which separates proteins by size and charge to identify monoclonal proteins (M-proteins) 1
- Serum immunofixation electrophoresis (IFE), which identifies the specific type of immunoglobulin involved (IgG, IgA, IgM, or light chains) 1
- Serum free light chain assay (FLC), which measures kappa and lambda light chains and their ratio 1 Complete blood count (CBC) is also important to assess for cytopenias that might suggest progression to more serious conditions. For urine testing, a 24-hour urine protein electrophoresis (UPEP) and urine immunofixation are necessary to detect Bence Jones proteins (free light chains excreted in urine) 1. These tests are complementary because some monoclonal proteins may be detected in urine but not in serum, or vice versa. Once MGUS is diagnosed, these tests should be repeated periodically (typically annually) to monitor for progression to multiple myeloma or related disorders, as MGUS carries a risk of approximately 1% per year for progression to a malignant condition 1.
Other tests that may be useful in certain circumstances include:
- Bone marrow aspiration and biopsy to evaluate bone marrow plasma cell infiltration 1
- Imaging studies such as MRI or CT scans to evaluate lytic bone lesions 1
- Fluorescence in situ hybridization (FISH) to detect chromosomal abnormalities 1
- Serum viscosity and fundoscopy to assess for hyperviscosity syndrome 1
It is essential to note that the frequency of follow-up and the specific tests used may vary depending on the individual patient's risk factors and clinical presentation 1.
From the Research
MGUS Screening Tests
To screen for Monoclonal Gammopathy of Undetermined Significance (MGUS), the following tests are commonly used:
- Serum protein electrophoresis (SPEP) to detect and quantify monoclonal immunoglobulins in the blood 2, 3
- Urine protein electrophoresis (UPEP) to detect monoclonal immunoglobulins in the urine 2, 4
- Immunofixation electrophoresis (IFE) to confirm the presence of paraprotein and determine its heavy and light chain type 2
Blood Tests
The following blood tests are used to screen for MGUS:
- Complete Blood Count (CBC) to evaluate blood cell counts
- Blood chemistry tests to evaluate kidney and liver function
- Serum protein electrophoresis (SPEP) to detect and quantify monoclonal immunoglobulins in the blood 3
- Immunofixation electrophoresis (IFE) to confirm the presence of paraprotein and determine its heavy and light chain type 2
Urine Tests
The following urine tests are used to screen for MGUS:
- Urine protein electrophoresis (UPEP) to detect monoclonal immunoglobulins in the urine 2, 4
- Urine immunofixation electrophoresis (UIFE) to confirm the presence of paraprotein and determine its heavy and light chain type
Additional Tests
Additional tests may be ordered to confirm the diagnosis of MGUS and rule out other conditions, such as:
- Bone marrow biopsy to evaluate bone marrow plasma cells 3, 5
- Skeletal survey to evaluate bone lesions 5
- Imaging studies, such as X-rays or MRI, to evaluate bone lesions
Test Interpretation
The results of these tests are used to diagnose MGUS and differentiate it from other conditions, such as multiple myeloma 4, 3, 6, 5. The presence of an M-spike in serum or urine electrophoresis is a key diagnostic criterion for MGUS 4, 3. However, the interpretation of these tests requires careful consideration of the clinical context and other diagnostic criteria 5.