Multiple myeloma will strike over 20,000 people in the United States each year, the Leukemia and Lymphatic Society reported in 2010. Multiple myeloma, a type of blood cell cancer, develops in plasma cells, a type of white blood cell. Plasma cells, normally found in the bone marrow, make antibodies and also produce osteoclast activating factor, which helps bone maintenance by breaking down old bone. When abnormal amounts of antibodies are produced, abnormal proteins appear in the urine and blood. In the urine, these proteins are called Bence-Jones proteins, named after their discoverer.
Cause
Proteins are normally too large to filter through the kidneys and appear in the urine. The appearance of protein in the urine often indicates a problem with the kidneys. Bence-Jones proteins, however, are very small and pass easily through the kidney filters. Between 50 and 80 percent of people with multiple myeloma have Bence-Jones proteins in their urine, according to the Gale Encyclopedia of Medicine.
Testing
Bence-Jones proteins cannot be detected on a normal urinalysis; a special test must be run. If your medical practitioner suspects multiple myeloma based on symptoms, he may look for Bence-Jones proteins. The screening test for Bence-Jones proteins requires only a regular urine sample. To determine the exact amount of protein in the urine, which is helpful to evaluate the severity of multiple myeloma, the screening test requires that all urine produced over a 24-hour period be collected in a large sterile plastic jug. Heating the urine to 140 F in the laboratory causes the proteins to clump together. Heating the urine too high causes the proteins to disappear, but they reappear as the urine cools. This test is not diagnostic and should be followed with a 24-hour collection and further testing, Jacques Wallach reports in "Interpretation of Diagnostic Tests."
Grading
Two more advanced tests, a urine protein electrophoresis and urine immunofixation electrophoresis are done to determine the exact amount of protein present to help determine the stage of the disease. The disease is rated from Stage I to Stage III, with Bence-Jones proteins being one part of the equation to determine staging along with other blood levels.
Caveat
Several other disorders can cause a false-positive result on the Bence-Jones protein test. Rheumatoid arthritis, systemic lupus erythmatosus and other autoimmune diseases can cause an initial false-positive reading. Taking high doses of penicillin and aspirin can also give a false-positive result on the screening test, which is why Wallach states that the screening test alone is not suitable for diagnosing multiple myeloma.
