Anti-Proteinase 3 Antibody (PR3)

Alternative name:
Description: The archetypal c-ANCA antigen is a serine proteinase termed proteinase 3, a 28kDa protein. Autoantibodies recognise primarily conformational epitopes. An improved assay (termed Pr3S) was introduced May 16 2011. Quantitative values using the new assay may vary significantly from those obtained previously
Indication: Specific autoantibodies in ANCA vasculitis particularly Wegeners granulomatosis.
Interpretation: c-ANCA antibodies usually recognising proteinase 3 are found in >90% patients with Wegeners granulomatosis. The levels of anti-Pr3 in any patient correlate with disease activity and usually disappear on effective treatment reappearing on reemergence of the disease. Patients with higher levels of anti-Pr3 on diagnosis do not necessarily have more serious disease.Anti-Pr3 is also found in 30% patients with microscopic polyarteritis or Churg Strauss syndrome but very seldom in other vasculitides. Rarely, low levels of anti-Pr3 sometimes with anti-MPO are detected in patients without vasculitis.
Sample: Serum Separator Tube (SST)
Assay details: Fluorescence enzyme linked immunoassay (Phadia Immunocap 250). Purified human Pr3 protein IgG antibodies.
Reference range: Post 15 May 2011: PR3S Pre 15 May 2011: PR3 <7U/ml
Assay range notes: Post 15 May 2011:
PR3S 2-3 IU/ml: equivocal
>3IU/ml: positive
Assay range: 0-170IU/ml
Pre 15 May 2011:
Pr3 7-10U/ml: equivocal
>10U/ml: positive
Assay range: 0.6 to 530U/ml
Turnaround time: 5-7 days
Analysing laboratory: Immunology The James Cook University Hospital