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Glomerular Basement Membrane Antibody

Anti-GBM antibody disease is a disorder in which circulating autoantibodies bind to the glomerular basement membrane (GBM), causing rapidly progressive cresentic glomerulonephritis. This disorder is also called Goodpasture's syndrome and Goodpasture's disease.

Anti-GBM antibody disease is most often idiopathic, but sometimes occurs after pulmonary infection or injury. The development of anti-GBM antibodies may precede the onset of clinical signs and symptoms by many months. Anti-GBM presents as acute renal failure with a urinalysis showing proteinuria, dysmorphic red cells, white cells, and red cell and granular casts. Approximately 50% of patients also have alveolar hemorrhage.

The principal target for the anti-GBM antibodies is the NC1 domain of the alpha-3 chain of type IV collagen. Alpha-3 chain is highly expressed in the glomerular and alveolar basement membranes. Patients with and without alveolar hemorrhage have the same autoantibody. Alveolar hemorrhage is more likely in patients in whom the alpha-3 chain antigen is exposed due to previous pulmonary injury such as smoking, infection, cocaine inhalation, or hydrocarbon exposure. Autoreactive T cells may also contribute to the development of glomerular and alveolar injury. There is some evidence of a genetic association with HLA-DR2.

The diagnosis of anti-GBM antibody disease requires demonstration of anti-GBM autoantibodies either in the serum or a kidney biopsy. Serum autoantibodies are detected using a direct enzyme-linked immunoassay that uses native or recombinant human alpha-3(IV) antigens. Sensitivity of these assays ranges from 87 to 95% and specificity from 91 to 100%.

Reference range is a negative result. Positive results are consistent with anti-GBM antibody disease.

Specimen requirement is one red top or SST tube of blood.

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