BPI-ANCA – IgG and IgA

Indication

Follow-up of patients with cystic fibrosis. Suspicion of infl ammatory diseases with ANCA or follow-up of positive IIF-ANCA.

Method

ELISA with purified BPI (bactericidal/permeability-increasing protein) from human granulocytes. BPI is a 55kD protein from azurophilic granules in granulocytes and is one of the most important proteins in these cells.

Answer

The result is given as arbitrary units after comparison with a standard serum. The analysis measures IgG antibodies and IgA antibodies.

Reference range

BPI-ANCA IgG: 38 with a borderline value 50. BPI-ANCA IgA: 53 with a borderline value 67.

Interpretation

Cystic fibrosis is a genetically conditioned disease, where a defect ion channel in the airway epithelium causes tough mucus. The tough mucus is colonized by bacteria.

In children staphylococci and other Gram-positive bacteria dominate, but at older ages Pseudomonas aeruginosa becomes the dominant pathogen. The prognosis forcystic fibrosis is varying. Some patients lose lung function rapidly, whereas others remain relatively unaffected high up in adulthood despite chronic bacterial colonization.

As a rule the colonization by Paeruginosa is established with cultivation but can be detected earlier using serology (antibodies against the bacteria). The antibody level correlates with the quantity of bacteria in the airways. For unknown reasons many patients have autoantibodies against BPI, i.e. BPIANCA. IgG-BPI-ANCA is the most common and may occur in up to 90% of the patients. IgA-BPI-ANCA is found in about 40%. There is a very strong correlation between BPI-ANCA and the colonization by Paeruginosa. Within the group of patients colonized by Paeruginosa, a high level of BPI-ANCA is associated with serious lung damage. It has been found that positive IgA-BPI-ANCA is a risk factor for respiratory insufficiency within five years.

IgA-BPI-ANCA has a stronger correlation with lung function impairment and Paeruginosa colonization than IgG-BPI-ANCA. BPI-ANCA also occurs in inflammatory bowel diseases and in some patients with vasculitis.

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Packages and other tests

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Acute test