Cryoglobulinemia

Definition

Bence Jones proteins are small proteins (light chains of immunoblobulin) found in the urine. Testing for these proteins is done to diagnose and monitor multiple myeloma and other similar diseases.

Purpose

Bence Jones proteins are considered the first tumor marker. A tumor marker is a substance, made by the body, that is linked to a certain cancer, or malignancy. Bence Jones proteins are made by plasma cells, a type of white blood cell. The presence of these proteins in a person's urine is associated with a malignancy of plasma cells.

Multiple myeloma, a tumor of plasma cells, is the disease most often linked with Bence Jones proteins. The amount of Bence Jones proteins in the urine indicates how much tumor is present. Physicians use Bence Jones proteins testing to diagnose the disease as well as to check how well the disease is responding to treatment.

Other diseases involving cancerous or excessive growth of plasma cells or cells similar to plasma cells can cause Bence Jones proteins in the urine. These diseases include: Waldenström's macroglobulinemia, some lymphomas and leukemias, osteogenic sarcoma, cryoglobulinemia, malignant B-cell disease, amyloidosis, light chain disease, and cancer that has spread to bone.

Description

Urine is the best specimen in which to look for Bence Jones proteins. Proteins are usually too large to move through a healthy kidney, from the blood into the urine. Bence Jones proteins are an exception. They are small enough to move quickly and easily through the kidney into the urine.

A routine urinalysis will not detect Bence Jones proteins. There are several methods used by laboratories to detect and measure these proteins. The classic Bence Jones reaction involves heating urine to 140°F (60°C). At this temperature, the Bence Jones proteins will clump. The clumping disappears if the urine is further heated to boiling and reappears when the urine is cooled. Other clumping procedures using salts, acids, and other chemicals are also used to detect these proteins. These types of test will reveal whether or not Bence Jones proteins are present, but not how much is present.

A more complex procedure is done to measure the exact amount of Bence Jones proteins. This procedure--immunoelectrophoresis--is usually done on urine that has been collected for 24-hours.

The test is covered by insurance when medically necessary. Results are usually available within several days.

Preparation

Urine is usually collected throughout a 24-hour time period. A person is given a large container in which to collect the urine. The urine should be refrigerated until it is brought to the laboratory or physician's office.

Normal results

Bence Jones proteins normally are not present in the urine.

Abnormal results

Bence Jones proteins are present in 50-80% of people with multiple myeloma. People with other malignancies also can have a positive Bence Jones proteins test, but less frequently.

Certain nonmalignant diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and chronic renal insufficiency, can have Bence Jones proteins in the urine. High doses of penicillin or aspirin before collecting the urine can give a false positive result.

Key Terms

Bence Jones protein

Small protein, composed of a light chain of immunoglobulin, made by plasma cells.

Multiple myeloma

A tumor of the plasma cells.

Plasma cells

A type of white blood cell.

Further Reading

For Your Information

Books

• Fischbach, Francis. A Manual of Laboratory and Diagnostic Tests, 5th ed. Philadelphia: Lippincott, 1996.
• Henry, John B., ed. Clinical Diagnosis and Management by Laboratory Methods, 19th ed. Philadelphia: W.B. Saunders, 1996.
• Pagana, Kathleen D. and Timothy J. Pagana. Mosby's Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby, 1998.

Gale Encyclopedia of Medicine. Gale Research, 1999.