The measurement of beta-2 microglobulin is used to evaluate the severity and prognosis of multiple myeloma, chronic lymphocytic leukemia, and non-Hodgkin lymphoma as well as to assess renal damage and to distinguish between glomerular and tubular renal disorders.
Beta-2 microglobulin is a protein that is found on the surface of all cells. It is a major histocompatibility HLA antigen and is found in increased numbers in white blood cells and in particular in lymphocytes. Production of beta-2 microglobulin increases as these cells replicate or are destroyed. Thus, beta-2 microglobulin is elevated in patients with malignancies (especially with B cell lymphoma, leukemia, or multiple myeloma), chronic infections, and severe chronic inflammatory diseases. The measurement of beta-2 microglobulin is an accurate estimate of the activity of the malignancy, the stage of the disease, and its prognosis and is, therefore, an important cancer marker.
The beta-2 microglobulin passes freely through the membrane of the glomerulus and is almost completely absorbed by the proximal tubular kidney cells. Due to extensive tubular resorption, under normal conditions, a very small amount of beta-2 microglobulin is eventually excreted in the urine. Therefore, the increased secretion of beta-2 microglobulin is indicative of impaired proximal tubule function. Thus, the measurement of beta-2 microglobulin is useful in differentiating between different types of kidney disease. In patients with aminoglycoside toxicity, heavy metal nephrotoxicity, or renal tubular damage, urinary beta-2 microglobulin levels are elevated. Excretion of beta-2 microglobulin is increased from 100 to 1000-fold above normal levels in cadmium-exposed workers.
The measurement of beta-2 microglobulin is particularly useful in the differential diagnosis of kidney disease. If blood and urine levels are measured simultaneously, the glomerular lesions may differ from those of the renal tubules. In glomerular disease, due to poor glomerular filtration, blood levels of beta-2 microglobulin are high and urine levels are low. In tubular disease, due to poor tubular resorption, blood levels of beta-2 microglobulin are low and urine levels are high. Blood levels of beta-2 microglobulin increase in the early stage of renal transplant rejection.
Possible Interpretations of Pathological Values
- Increase: Lymphomas, leukemia, myeloma, renal glomerular disease, renal transplant rejection, viral infections especially with HIV and cytomegalovirus, chronic inflammatory processes.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
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