Alternative Names: GBM antibody test; Antibody to human glomerular basement membrane

How the test is performed:

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test:

No special preparation is necessary.

Infants and children:

The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

This test is used when the presence of antibodies against the glomerular basement membrane (part of the kidney filtering system) is suspected as the cause of kidney disease.

Immunologically-mediated kidney diseases may involve autoantibodies (antibodies against the body's own tissue) directed against kidney antigens; or it may involve immune complexes of autoantibodies (an antibody and� antigen combine to form a complex) that become deposited in the filtering system of the kidneys. In the first case, formation of antibodies against the basement membrane of the filtering system results in damage to the basement membrane and kidney failure.

Normal Values:

No presence of antibodies.

What abnormal results mean:

• Goodpasture's syndrome, a rare disease involving the lungs and kidney. It results in bleeding into the lungs and is almost invariably fatal if untreated.
• acute nephritic syndrome
• rapidly progressive (crescentic) glomerulonephritis

What the risks are:

• excessive bleeding
• fainting or feeling light-headed
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations:

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.