Beta-2 Microglobulin

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Also known as: B2M; β2-Microglobulin; Thymotaxin
Formal name: Beta2 Microglobulin, Serum, Urine or CSF

At a Glance

Why Get Tested?

To help evaluate the severity and prognosis of multiple myeloma, leukaemia, or lymphoma; to distinguish between kidney disorders and to detect kidney damage

When to Get Tested?

When you have been diagnosed with multiple myeloma or certain other cancers; sometimes to monitor treatment; when you have signs associated with kidney dysfunction

Sample Required?

A blood sample drawn from a vein in your arm; sometimes a 24-hour urine sample; rarely a cerebrospinal fluid (CSF) sample

Test Preparation Needed?


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 myelomaleukaemia, 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 leukaemia 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.

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

No test preparation is needed

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.