Urine immunofixation is a laboratory technique used to identify proteins in urine.

Collect a "clean-catch" (midstream) urine sample. To obtain a clean-catch sample, men or boys should wipe clean the head of the penis. Women or girls should wash the area between the labia (lips of the vagina) with soapy water and rinse well.

As you start to urinate, allow a small amount to fall into the toilet bowl. This clears the urethra -- the tube that carries urine from the bladder. Then, in a clean container, catch about 1 to 2 ounces of urine, and remove the container from the urine stream. Give the container to the health care provider or assistant.

For an infant:

Thoroughly wash the area around the opening of the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Place a diaper over the infant (bag and all).

Check your baby frequently and remove the bag after the infant has urinated into it. For active infants, this procedure may take a couple of attempts -- lively infants can displace the bag, causing an inability to obtain the specimen. The urine is drained into a container for transport back to the health care provider.

No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

The test involves only normal urination, and there is no discomfort.

The main reason this test is done is to identify and monitor substances called monoclonal immunoglobulins. These substances occur in persons with diseases such as multiple myeloma and Waldenstrom's macroglobulinemia.

No presence of monoclonal immunoglobulins is normal.

Usually, abnormal results indicate immune system disorders including multiple myeloma and Waldenstrom's macroglobulinemia.

Sometimes monoclonal immunoglobulins are present, but no evidence of these conditions can be found.

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

McPherson RA and Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: WB Saunders; 2007:845-6.

Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston; 2005:727-33.