Immunofixation - urine

Definition

This is a laboratory technique used to identify proteins in urine.

How the test is performed

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 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 of contaminants.) 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 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.

Immunofixation is a laboratory technique that is used to enhance the results of standard protein electrophoresis. With protein electrophoresis, the urine is placed on specially treated paper and exposed to an electric current. The various proteins migrate (move on the paper) to form bands that indicate the relative proportion of each protein fraction.

Immunoglobulins (antibodies) appear as a "gamma" band. Immunofixation is a technique to separate this "gamma" band and identify the individual immunoglobulins. It is similar to immunoelectrophoresis, but it may give more rapid results and is more sensitive.

How to prepare for the test

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.

How the test will feel

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

Why the test is performed

The primary use of immunofixation is the identification and monitoring of monoclonal proteins (that is, IgG, IgM, IgA, lambda light chain, and kappa light chain), including those that are present in multiple myeloma and Waldenstrom's macroglobulinemia.

Normal Values

No presence of monoclonal immunoglobulins is normal.

What abnormal results mean

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

Sometimes monoclonal immunoglobulins are present, but no evidence of malignancy (cancer) can be found.

Illustrations

Female urinary tract

Male urinary tract