Beta 2 Microglobulin
Beta 2microglobulin is expressed on the surface of almost all nucleated cells as a subunit of class I major histocompatibility complex molecules. Beta 2 microglobulin is normally shed into the circulation in low concentration, freely filtered across the glomerular basement membrane, and almost completely reabsorbed by proximal tubular cells in the kidney. Plasma concentrations increase in diseases associated with increased cell turnover such as chronic lymphocytic leukemia, lymphoma and multiple myeloma.
Beta 2 microglobulin level is elevated in the plasma of 75% of patients with multiple myeloma at the time of diagnosis. Patients with serum beta 2 microglobulin levels less than 4 ug/ml have a better prognosis than those with levels greater than 4 ug/mL. The prognostic value of serum beta 2 microglobulin levels is probably related to two factors:
- High levels are associated with greater tumor burden.
- High levels are associated with renal failure
Beta 2 microglobulin plasma levels may also be increased in patients with chronic inflammation, liver disease, acute viral infections, and solid tumors.
In renal tubular disease, serum levels of beta 2 microglobulin are decreased and urine levels are increased. Proximal tubule injury can be caused by exposure to cadmium, mercury, lithium, or aminoglycosides.Workers exposed to cadmium may have urine levels that are 100 to 1000 times higher than normal. Urine results must be interpreted with caution because beta 2 microglobulin is unstable at pH <6.0.
Beta 2 microglobulin is measured by nephelometry. Serum specimen requirement is a red top tube of blood. Urine measurement requires 1mL of urine.
Serum reference range is 1.20 - 2.70 ug/mL. Urine reference range is 0 to 300 ug/L.
References
Bataille R, Magub M, Grenier J, et al: Serum beta-2-microglobulin in multiple myeloma: Relation to presenting features and clinical status. Eur J Cancer Clin Oncol 1982;18:59-66
2. Garewal H, Durie BG, Kyle RA, et al: Serum beta-2-microglobulin in the initial staging and subsequent monitoring of monoclonal plasma cell disorders. J Clin Oncol 1984;2:51-57
3. Norfolk D, Child JA, Cooper EH, et al: Serum beta-2-microglobulin in myelomatosis: potential value in stratification and monitoring. Br J Cancer 1980;42:510-550
4. Dolan MJ, Lucey DR, Hendrix CW, et al: Early markers of HIV infection and subclinical disease progression. Vaccine 1993;11:548-551
5. Karlsson FA, Wibell L, Evrin PE: Beta-2-microglobulin in clinical medicine. Scand J Clin Lab Invest 1986;154:27-37
