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Introduction ⬇

Urine β2-Microglobulin

β2-Microglobulin, an amino acid peptide component of the lymphatic human lymphocyte antibody (HLA) major histocompatibility complex, is found on the outside of the plasma membrane. It is structurally related to the immunoglobulins.

This test measures β2-microglobulin, which is nonspecifically increased in inflammatory conditions and in patients with malignancies (e.g., lymphoma, active chronic lymphatic leukemia, or multiple myeloma). It may be used to differentiate glomerular from tubular dysfunction. In glomerular disease, β2-microglobulin is increased in serum and decreased in urine, whereas in tubular disorders, it is decreased in serum and increased in urine. In aminoglycoside toxicity, β2-microglobulin levels become abnormal before creatinine levels begin to show abnormal values. Serum is also used to evaluate the prognosis of multiple myeloma.

Normal Findings ⬆ ⬇

Urine 24-hour specimen: <1 mg/24 hr or <1 mg/d

Blood serum specimen: <2.7 μg/mL or <2.7 mg/L

Procedure ⬆ ⬇

  1. Collect a 24-hour urine specimen or a serum sample (~5 mL).

  2. Keep the pH neutral or alkaline (pH >6.0).

  3. Freeze specimen if not analyzed immediately. Not stable at room temperature.

Clinical Implications ⬆ ⬇

  1. Increased urine β2-microglobulin occurs in:

    1. Renal tubular disorders (>50 mg/24 hr or >50 mg/d)

    2. Heavy metal poisoning (mercury, cadmium)

    3. Drug toxicity (aminoglycosides, cyclosporine)

    4. Fanconi syndrome

    5. Wilson disease

    6. Pyelonephritis

    7. Kidney allograft rejection

    8. Lymphoid malignancies associated with B-lymphocyte lineage

    9. AIDS (can be used as a predictor of the progression to AIDS)

  2. Increased serum β2-microglobulin occurs in:

    1. Multiple myeloma

    2. Amyloidosis

    3. Viral infection

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain purpose of test, procedure for 24-hour urine collection, and interfering factors.

  2. See instructions for 24-hour urine collection (see Long-Term, Timed Urine Specimen [2-Hour, 24-Hour]).

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Monitor appropriately.

  2. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

  1. Acid urine.

  2. Certain antibiotics (e.g., gentamicin, tobramycin).

  3. Recent nuclear medicine scan.

  4. Increased synthesis in certain diseases (e.g., Crohn disease, hepatitis, sarcoidosis) decreases the usefulness of the blood serum test.

  5. Random specimens are not recommended.