Immunofixation - urine

Definition

Urine immunofixation is a test to look for abnormal proteins in urine.

How the Test is Performed

You will need to supply a clean-catch (midstream) urine sample.

• Clean the area around where urine leaves the body. Men or boys should wipe the head of the penis. Women or girls should wash the area between the lips of the vagina with soapy water and rinse well.
• Allow a small amount to fall into the toilet bowl as you start to urinate. This clears substances that may contaminate the sample. Catch about 1 to 2 ounces (30 to 60 milliliters) of urine in the clean container that you are given.
• Remove the container from the urine stream.
• Give the container to the health care provider or assistant.

For an infant:

• Thoroughly wash the area where the urine exits the body.
• Open a urine collection bag (a plastic bag with an adhesive paper on one end).
• For males, place the entire penis in the bag and attach the adhesive to the skin.
• For females, place the bag over the labia.
• Diaper as usual over the secured bag.

It may take more than one try to get a sample from an infant. An active baby can move the bag, so that the urine goes into the diaper. Check the infant often and change the bag after the urine has been collected. Drain the urine from the bag into the container given to you by your provider.

Deliver the sample to the lab or your provider as soon as possible after it is done.

How to Prepare for the Test

No special steps are necessary for this test.

How the Test will Feel

The test involves only normal urination. There is no discomfort.

Why the Test is Performed

This test is most often used to check for the presence of certain proteins called monoclonal immunoglobulins. These proteins are linked to multiple myeloma and Waldenström macroglobulinemia. The test is also done with a blood test to check for a monoclonal immunoglobulin in the serum.

Normal Results

Having no monoclonal immunoglobulins in the urine is a normal result.

What Abnormal Results Mean

The presence of monoclonal proteins may indicate:

• Cancers that affect the immune system, such as multiple myeloma or Waldenström macroglobulinemia
• Other cancers

Considerations

Immunofixation is similar to urine immunoelectrophoresis, but it may give more rapid results.

References

McPherson RA, Riley RS, Massey HD. Laboratory evaluation of immunoglobulin function and humoral immunity. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 46.

Treon SP, Castillo JJ, Hunter ZR, Merlini G. Waldenström macroglobulinemia/lymphoplasmacytic lymphoma. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 87.