From the Guidelines
Urine Beta-2 Microglobulin (β2M) is a protein marker that reflects tumor mass and is used as a standard measure of tumor burden in multiple myeloma. This protein is normally present in small amounts in urine, and elevated levels can indicate kidney tubule damage or dysfunction, particularly in the proximal tubules 1. The level of beta2 microglobulin is considered a sensitive marker for early detection of kidney injury, often before other traditional tests show abnormalities.
Key Points
- Urine Beta-2 Microglobulin (β2M) is a low molecular weight protein that is freely filtered by the glomeruli and almost completely reabsorbed by healthy proximal tubules.
- When tubular function is impaired, more of this protein appears in the urine, making it a useful indicator of tubular health.
- The test is typically performed on a urine sample, and normal levels are generally below 0.3 mg/L, but specific reference ranges may vary by laboratory.
- Elevated levels warrant further investigation and may indicate conditions such as diabetic nephropathy, heavy metal poisoning, or other forms of kidney disease.
- This test is often used in conjunction with other kidney function tests for a comprehensive assessment, particularly in monitoring patients at risk for kidney disease or those undergoing potentially nephrotoxic treatments 1.
Clinical Use
- Urine Beta-2 Microglobulin (β2M) is used to assess kidney function and detect early signs of kidney damage.
- It is also used as a prognostic factor in multiple myeloma, with higher levels indicating a poorer prognosis.
- The test is useful in monitoring disease response and progression in patients with multiple myeloma, particularly those with non-secretory myeloma.
From the Research
Definition and Function of Urine Beta-2 Microglobulin (β2M)
- Urine Beta-2 Microglobulin (β2M) is a protein that is constantly produced in the body and eliminated almost exclusively by the kidneys 2.
- It is predominantly filtered by the glomeruli and then reabsorbed and catabolized in the kidney tubules, with more than 99.9% of the excreted protein being reabsorbed 2.
Role of β2M as a Biomarker
- β2M can serve as a biomarker for renal function and disease, with elevated levels indicating proximal tubular dysfunction or decreased glomerular filtration rate (GFR) 2, 3, 4.
- An increased excretion of β2M in the urine is a sensitive indicator of proximal tubular dysfunction in many clinical conditions 2.
- β2M levels can also be used to assess renal allograft function and detect potential renal damage in transplant recipients 4.
Clinical Significance of β2M
- Elevated serum β2M levels are seen in renal diseases, dialysis patients, chronic inflammatory diseases, and certain malignancies 5.
- Urinary β2M levels can be used to distinguish between tubulointerstitial and glomerular diseases, with a higher ratio of urinary β2M to total protein concentration indicating tubulointerstitial disease 6.
- A ratio of urinary β2M to total protein concentration of < 22.3 μg/mg may indicate the presence of glomerular disease 6.