Anti-glomerular basement membrane antibody (Anti-GBM)

Alternative name:
Description: Goodpasture’s syndrome is an autoimmune condition characterised by rapidly progressive glomerulonephritis accompanied by pulmonary haemorrhage. It is caused by antibodies to the glomerular and alveolar basement membranes. Anti-GBM antibody-induced glomerulonephritis is responsible for about 5% of human glomerulonephritides.The antibodies which are pathogenic are usually IgG. Anti-GBM antibodies are a highly sensitive and specific marker of Goodpasture’s syndrome. Levels correlate with disease activity and often predict clinical outcome. In kidney sections, these autoantibodies show linear distribution in the GBM, Bowmans capsule, and distal tubular basement membranes, but not of proximal tubules. The same antigen is found in basement membranes of the alveoli, and choroid plexus, and to membranes of the lens capsule, choroid, and retina of the eye and cochlea, but not in other organs.The antigen is on the globular domain of subendothelial collagen type IV; specifically the 30kDa M2 subunit. Glomerular Type IV collagen contains unique types of collagen chain termed α3 and α4; six types of α-chain have been identified in other basement membranes. NC1 domains of the various a-chains are released as hexamers by collagenase digestion of GBM. This is the antigen used in our assay.
Indication: Goodpasture’s syndrome, unexplained renal/lung disease (pulmonary renal syndrome). Unexplained rapidly progressive glomerulonephritis (RPGN) without lung involvement (GBM disease). Diagnosis of Goodpasture’s disease. The diagnosis can be confirmed by renal biopsy immunofluorescence which detects the same autoantibodies in situ.
Interpretation: Anti-GBM antibodies are found in the sera of the majority of patients with Goodpastures syndrome affecting kidney and lung but occasionally only the kidney. Serum antibodies are sometimes not detected in Goodpastures even though the antibodies are detected in situ upon kidney biopsy. Less than 2% of patients with glomerulonephritis have these autoantibodies.A subset of patients with rapidly progressive glomerulonephritis has been identified who have both anti-GBM and ANCA. These patients tend to have lower levels of anti-GBM and better renal prognosis.
Sample: Serum Separator Tube (SST)
Assay details: Fluorescence enzyme linked immunoassay (Phadia Immunocap 250). Human recombinant a3 chain of collagen IV: IgG antibodies
Reference range: < 7IU/mL
Assay range notes: GBM 7-10U/ml: equivocal
>10U/ml: positiveAssay range: 0.8 to >680U/ml
Turnaround time: 5 – 7 days
Analysing laboratory: Immunology The James Cook University Hospital