Type of test Urine

 Normal findings

 Kappa total light chain: < 0.68 mg/dL Lambda total light chain: < 0.4 mg/dL Kappa/lambda ratio: 0.7-6.2

Test explanation and related physiology

 The detection of Bence Jones protein in the urine most commonly indicates multiple myeloma (especially when the urine levels are high). The test is used to detect and monitor the treatment and clinical course of multiple myeloma and other similar globulin diseases.

 Bence Jones proteins are monoclonal light-chain portions of immunoglobulins found in 75% of patients with multiple myeloma. These proteins are made most notably by the plasma cells in these patients. They also may be associated with tumor metastases to the bone, chronic lymphocytic leukemias, lymphoma, macroglobulinemia, and amyloidosis.

 Immunoglobulin light chains are usually cleared from the blood through the renal glomeruli and are reabsorbed in the proximal tubules; thus urine light-chain concentrations are normally very low or undetectable. The production of large amounts of monoclonal light chains, however, can overwhelm this reabsorption mechanism. Because the Bence Jones protein is rapidly cleared from the blood by the kidneys, it may be very difficult to detect in the blood; therefore urine is used for this study. Normally urine should contain no Bence Jones proteins.

 Routine urine testing for proteins using reagent strips often does not reflect the type or amount of proteins in the urine. In fact, the strip may show a completely negative result despite large amounts of Bence Jones globulins in the urine. Proteins in the urine are best identified by protein electrophoresis of the urine and then are identified and quantified (immunofixation). Monitoring the urine M-spike (a spike on electrophoresis indicating multiple myeloma) is especially useful in patients with light-chain mul tiple myeloma in whom the serum M-spike may be very small or absent but in whom the urine M-spike is large.

 Interfering factors

• Dilute urine may yield a false-negative result.

* High doses of aspirin or penicillin can cause false-positive results.

Procedure and patient care

 • See inside front cover for Routine Urine Testing.

- Instruct the patient to collect an early morning specimen of at least 50 mL of uncontaminated urine in a container. It may be helpful to know the amount of these proteins excreted over 24 hours. If so, a 24-hour collection is ordered.

• Immediately transport the specimen to the laboratory. If it cannot be taken to the laboratory immediately, refrigerate it. Heat-coagulable proteins can decompose, causing a false- positive test.

Abnormal findings

Increased levels

- Multiple myeloma (plasmacytoma)

- Various metastatic tumors

- Chronic lymphocytic leukemia

- Amyloidosis

- Lymphoma

- Waldenström macroglobulinemia

- Osteogenic sarcoma

- Cryoglobulinemia

- Rheumatoid diseases