Tests to assess monoclonal protein

This important group of blood and urine tests is used to assess the amount and activity of myeloma. These tests measure the monoclonal protein that myeloma cells secrete into the blood and/or urine.

Serum Quantitative Immunoglobulins (QIg) 

REFERENCE RANGE for patients ≥ 18 years old 

IgG 767–1,590 mg/dL 

IgA 61–356 mg/dL 

IgD ≤ 10 mg/dL 

IgE ≤ 214 mg/dL 

IgM 37–286 mg/dL 

QIg testing measures the total amount of each primary immunoglobulin or antibody class (also called an “isotype”) in the serum. It measures both polyclonal (normal) and monoclonal (myeloma-related) immunoglobulins. If an increase in one of the antibody isotypes is found, further testing with electrophoresis is required. This testing can determine if the elevation is caused by the presence of monoclonal immunoglobulin protein.  

IgA may be difficult to quantify with electrophoresis. That’s why QIg is often the preferred way to assess IgA protein. Note: The ranges for IgD and IgE are reported differently from those for IgG, IgA, and IgM. 

Isotypes of immunoglobulins

kappa	lambda
IgG kappa	IgG lambda
IgA kappa	IgA lambda
IgM kappa	IgM lambda
IgD kappa	IgD lambda
IgE kappa	IgE lambda

Serum Protein Electrophoresis (SPEP) 

REFERENCE RANGE 

albumin 3.3–5.7 g/dL 

alpha-1 0.1–0.4 g/dL 

alpha-2 0.3–0.9 g/dL 

beta-2 0.7–1.5 g/dL 

gamma 0.5–1.4 g/dL 

SPEP is one of the most important tests used to diagnose and assess the status of myeloma. It measures the amount of M-protein that is made by myeloma cells. The amount of M-protein production is linked to the number and/or activity of myeloma cells, except with non-secretory myeloma. 

SPEP separates and quantifies proteins based on their electrical charge, size, and shape. As you learned above, the two types of protein in serum are albumin and globulin. Although there is only one type of albumin, there are sub-types of globulin, usually appearing on SPEP as alpha-1,alpha-2, beta-1, beta-2, and gamma globulins. Immunoglobulin proteins are gamma globulins, and usually, M-protein produced by myeloma cells will separate out in the gamma region of the graph. The exception to this rule is IgA protein. This protein may sometimes migrate to the beta or even the alpha-2 region. If this occurs, other tests can be more useful than SPEP. 

Monoclonal immunoglobulin protein appears on the results graph as a narrow spike. Because all the cells in the M-protein are identical and have the same electrical charge, they gravitate to the same small gamma region and form a peak or spike on the graph. The M-spike is the telltale indicator of myeloma protein in the blood, a marker for the activity of myeloma cells. By calculating the area under the curve (AUC) of the spike and then subtracting the amount representing normal immunoglobulins, the pathologist can quantify the amount of M-protein. 

Serum albumin accounts for 55% of the total protein in the clear liquid part of the blood and is produced in the liver. When myeloma is active,it stimulates the production of certain cellular proteins (cytokines). These cytokines impede the ability of the liver to produce albumin, and the level of albumin in the serum drops. According to the revised International Staging System (R-ISS), albumin is one of two blood proteins used to predict the behavior of myeloma cells at diagnosis. The other blood protein is serum beta-2 microglobulin (β2-microglobulin, β2M, or β2M). 

SPEP test result examples:

 

Urine Protein Electrophoresis (UPEP) 

REFERENCE RANGE 

globulins in the urine no significant amount 

total protein < 167 mg/24 hours 

urine albumin < 5 mg/dL 

Approximately 30% of myeloma patients have light chain protein in their urine as well as heavy chain protein in the blood. Approximately 15%–20% of patients have myeloma cells that produce only light chains and no heavy chains. Although fragments of heavy chain proteins can be found in the urine, intact heavy chains are too large to fit through the capillaries that send blood to the kidneys for filtration. Light chains, however, are so small and light in molecular weight (hence the name “light” chains). Because of their small size, they can easily pass through the capillaries and enter the kidneys. Then, they may move to the bladder and into the urine. 

Patients submitting a specimen for UPEP must collect urine for 24 hours. A 24-hour urine specimen provides a good indication of average amounts of different proteins in the urine. UPEP separates the proteins according to their size and electrical charge. Then, it quantifies the amount of light chain protein. 

Freelite® (serum free light chain assay) 

REFERENCE RANGE 

free kappa 3.3–19.4 mg/L 

free lambda 5.71–26.3 mg/L 

kappa/lambda ratio 0.26–1.65 

Immunoglobulins are made up of heavy chains and light chains. These heavy and light chains are usually bound together as “intact immunoglobulins.” Plasma cells produce more light chains than heavy chains. These unbound light chains circulate freely in the blood. These “free” light chains are present in both healthy individuals and in patients with myeloma. Healthy individuals have many intact antibody molecules circulating in their blood, but they have fewer free light chains. 

The Freelite test can show if the myeloma cells are releasing kappa free light chains at a high level and lambda light chains at a normal or lower level. The Freelite test can also show if the myeloma cells are secreting lambda free light chains at a higher level and kappa free light chains at a normal or lower level. 

Some patients’ myeloma cells secrete both heavy and light chains. Some secrete only heavy chains. Some secrete only light chains; this is called Bence-Jones myeloma. Some patients’ myeloma cells may secrete many more light chains at relapse than they did prior to treatment. 

Do not compare your Freelite results with other patients. Your Freelite results are a meaningful way to monitor your myeloma when the tests are tracked over time. 

Possible Freelite test results

Kappa/Lambda ratio (0.26 - 1.65)	Kappa (3.3-19.4 mg/L)	Lambda (5.7-26.3 mg/L)	Interpretation
Normal	Normal	Normal	No evidence of monoclonal light chains. Confirm with other lab tests.
High	High	Normal	Monoclonal kappa free light chains.
Low	Normal	High	Monoclonal lambda free light chains.
Normal	High	High	Plasma cells of both light chain types are secreting antibodies (possible infection, autoimmunity, or kidney damage).
Normal	Low	Low	General immense suppression (possibly due to chemotherapy or for other reasons).
High	Normal	Low	Possible low-level monoclonal kappa free light chains or immune suppression of lambda.
Low	Low	Normal	Possible low-level monoclonal lambda free light chains or immune suppression of kappa.
"Slightly" High	"Slightly" high	Normal or slightly high	Possible kidney damage ("slightly" = up to approximately 3.1).

Freelite is also used in the diagnosis and monitoring of patients with MGUS, and in monitoring patients with SMM. For more information, read the IMF’s booklet Understanding MGUS and Smoldering Multiple Myeloma. 

The Freelite test is useful for patients with any type of myeloma, including low secreting or non-secretory disease, and at different stages of myeloma, during treatment and after treatment. 

Hevylite® (serum heavy + light chain isotype assay) 

REFERENCE RANGE 

IgG kappa 4.03–9.78 g/L 

IgG lambda 1.97–5.71 g/L 

IgG kappa/IgG lambda ratio 0.98–2.75 

IgA kappa 0.48–2.82 g/L 

IgA lambda 0.36–1.98 g/L 

IgA kappa/IgA lambda ratio 0.80–2.04 

The Hevylite assay is a laboratory blood test for measuring intact immunoglobulins. 

According to the approval by the FDA, Hevylite is to be used for previously diagnosed myeloma along with other clinical and laboratory findings. 

While the Freelite test quantifies free light chains, the Hevylite test measures intact immunoglobulin heavy and light chain pairs involved in a patient’s myeloma. Hevylite results are calculated by a computer, eliminating the variations of individual subjectivity. 

Most myeloma patients’ cancer cells secrete an immunoglobulin comprised of both a single type of heavy chain and a single type of light chain. 

There is no difference in the way the various types of myeloma are treated. Yet, it’s important to know your type of heavy and light chain for monitoring purposes. 

Your myeloma cells are making the immunoglobulin pair. Also, you have normal, intact immunoglobulin pairs circulating in your bloodstream. The Hevylite test can distinguish between the “involved” proteins and “uninvolved” (normal) proteins.  

The involved proteins have the heavy and light chain produced by the myeloma. The “uninvolved” (normal) proteins have the same heavy chain isotype but are bound to a different light chain.  

For example, if you have IgG kappa myeloma (the “involved” heavy and light chain), then your IgG lambda heavy and light chain pairs are the normal “uninvolved” immunoglobulins. 

Hevylite is an extremely sensitive measurement of both myeloma protein and normal immunoglobulins. It is an accurate way to measure IgA myeloma. IgA often does not show up by SPEP. When Hevylite reveals that normal Ig levels are suppressed, it can be an early indicator of relapse. 

Hevylite can detect extremely low levels of M-protein. These low levels indicate the presence of minimal residual disease (MRD).