Blood test uses electricity to reveal myeloma's footprints

On Call

April 23, 1996|By Dr. Simeon Margolis | Dr. Simeon Margolis,Special to The Sun

My older brother was recently diagnosed with multiple myeloma. His several courses of treatment have been accompanied by blood tests, which are said to determine whether the treatments are working.

I would like to know how these blood tests work, and if I should get these tests in case the disease runs in families.

Multiple myeloma (or just myeloma) is an uncontrolled, malignant proliferation of plasma cells (blood cells that produce antibodies to protect against infections). The cancer results from the proliferation of exact copies of a single plasma cell, which secrete large quantities of an abnormal antibody into the blood.

The abnormal antibody can be identified by a protein electrophoresis test, which uses an electrical current to spread out the plasma proteins and detect it.

When increased amounts of a single antibody, or immunoglobulin, are present, they show up as a large, sharp peak, referred to as an M component. The quantity of the M component can be accurately measured by a more sophisticated protein test known as immuno- electophoresis. The amount of M component in the blood is a reliable marker of the number of cancerous plasma cells in the body. Measurements of a decline in the amount of M component in the blood correlate with the destruction of plasma cells during treatments.

Multiple myeloma is rare before the age of 40. Its incidence increases with age; the average age of patients is about 68 years. It accounts for about 1 percent of all cancers in whites and 2 percent in blacks. The most prominent symptom is usually bone pain, especially in the back and ribs, resulting from the expansion of plasma cells in the bone marrow. Bone destruction can produce high blood levels of calcium (hypercalcemia) and collapse of the spinal column. Hypercalcemia can cause weakness, lethargy, confusion and kidney damage. Spinal collapse can compress the spinal cord and produce difficulty with bladder and bowel function. Other common problems in patients with myeloma are anemia, recurrent infections (particularly pneumonia and kidney infections) and kidney failure.

Myeloma is treated with repeated courses of chemotherapeutic agents that help control, but not cure the disease. Recent studies have shown that bisphonates, such as alendronate, are effective in slowing the bone destruction and decreasing the bone pain.

You should not consider a blood test for M component for several reasons. In the first place, you are not at increased risk for myeloma because it is not an inherited disease. Secondly, an M component spike on plasma protein electrophoresis may signal a non-malignant condition known as benign monoclonal gammopathy. This benign condition is present in about 1 percent of those over 50 and 10 percent of individuals older than 75.

Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.

Pub Date: 4/23/96

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