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Beta-2 Microglobulin

Also known as: B2M; B2M; β2-Microglobulin; Thymotaxin
Formal name: Beta2 Microglobulin, Serum, Urine, or CSF
Related tests: Albumin, Tumor Markers, CSF Analysis

The Test Sample

What is being tested?

Beta2-microglobulin (B2M) is a protein that is found on the surface of almost all cells in the body. It is present in most body fluids and is increased in the blood with cancers such as multiple myeloma, leukemia, and lymphoma, and with inflammatory disorders. This test measures B2M in the blood, urine, or rarely in the cerebrospinal fluid (CSF).

In the kidneys, B2M passes through blood filtering units, the glomeruli, and is then reabsorbed by the renal tubules, structures which reclaim water, proteins, vitamins, minerals, and other substances that are useful to the body. Normally, only small amounts of B2M are present in the urine, but when the renal tubules become damaged or diseased, concentrations increase due to a decrease in resorption. In people with kidney disease who are undergoing dialysis, B2M can form long protein chains that can be deposited in joints and tissues, causing stiffness and pain. This condition is called B2M dialysis-associated amyloidosis.

B2M levels can be increased in the CSF of patients with blood cell cancers involving the brain, such as leukemia and lymphoma, but also with some chronic disorders such as multiple sclerosis, and with viral infections such as HIV.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. A 24-hour urine sample may also be collected. Rarely, a CSF sample may be collected by a doctor from the lower back using a procedure called a lumbar puncture or spinal tap.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.