Bence-Jones protein - quantitative

Definition

This test measures the presence of Bence-Jones proteins (free immunoglobulin light chains) in urine.

Normally, light chains (one component of antibodies) are produced in excess of heavy chains (the other component of antibodies). Increases in free light chains (polyclonal) may occur with increased immunoglobulin synthesis or catabolism (breakdown of cells and tissues).

These light chains do not exhibit the same characteristics of Bence-Jones proteins (monoclonal free-light chains). Immunofixation is the best test for detecting free monoclonal light chains.

How the test is performed

Collect a "clean-catch" (midstream) urine sample. To obtain a clean-catch sample, men or boys should wipe clean the head of the penis. Women or girls should wash the area between the labia with soapy water and rinse well.

As you start to urinate, allow a small amount to fall into the toilet bowl. (This clears the urethra of contaminants.) Then, in a clean container, catch about 1 to 2 ounces of urine, and remove the container from the urine stream. Give the container to the health care provider or assistant.

For an infant:

Thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Place a diaper over the infant (bag and all).

Check your baby frequently and remove the bag after the infant has urinated into it. For active infants, this procedure may take a couple of attempts -- lively infants can displace the bag, causing an inability to obtain the specimen. The urine is drained into a container for transport back to the health care provider

Since Bence-Jones proteins are relatively small, they can be filtered by the glomerulus (blood filtering unit of the kidney). When urine protein is elevated, and other clinical features suggest multiple myeloma, a Bence-Jones proteins test may be ordered. These proteins have an unusual thermal property that allows them to be identified. They precipitate from urine when heated to between 113 degrees and 140 degrees Fahrenheit and then re-dissolve on boiling. Definitive identification is made by immunoelectrophoresis.

How the test will feel

The test involves only normal urination, and there is no discomfort.

Why the test is performed

This test is performed to aid in the diagnosis of disorders that can cause protein in the urine (proteinuria).

Normal Values

No presence of Bence-Jones proteins is normal.

What abnormal results mean

Bence-Jones proteins are rarerly found in urine, but if they are, it is usually associated with multiple myeloma. Less commonly they are present in Waldenstrom's macroglobulinemia, chronic lymphocytic leukemia, or amyloidosis.

Illustrations

Male urinary system

Page Content:

Immunoglobulin light chains - urine; Urine Bence-Jones protein