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Vasculitis is a condition that causes inflammation of vessel walls.1 Vasculitis diseases are grouped based on the types of blood vessels or organs they affect, which can vary widely.1 One specific disease is anti-neutrophil cytoplasmic antibodies (ANCAs) associated vasculitis.2,3
The ANCA-associated vasculitides (AAV) are comprised of Granulomatosis with Polyangiitis (GPA, formerly Wegener's Granulomatosis), Microscopic Polyangiitis (MPA) and Eosinophilic Granulomatosis with Polyangiitis (EGPA, formerly Churg-Strauss Syndrome). They share the features of small vessel vasculitis but are otherwise a heterogeneous group with different preferences of organ involvement and frequency of ANCA positivity. In general, GPA and EGPA are characterized by granulomatous lesions (especially of the respiratory tract) and small to medium size vessel vasculitis in biopsy specimens, whereas MPA is a small to medium size vessel vasculitis without granuloma. PR3 and MPO ANCA are present in almost all patients with MPA and GPA in the active generalized stage of the disease; in EGPA, ANCA are present in less than 40% and their presence is associated with typical vasculitis manifestations such as glomerulonephritis.4
ANCA-associated vasculitis is rare and difficult to diagnose, but doing so is imperative. Early diagnosis has the capacity to produce a more favorable long-term outcome for patients with this serious disease.5
For several decades, ANCAs have been recognized as an important laboratory tool in the diagnosis of the small-vessel vasculitis. International guidelines recommend utilizing serology for ANCAs. These diagnostic tools can help your clinicians identify the disease and start their patients on the road to treatment for GPA, MPA, EGPA.4
Current guidelines can steer the testing process and help guide clinician’s diagnostic decision making.
The revised 2017 international consensus on testing of ANCAs in granulomatosis with polyangiitis and microscopic polyangiitis proposes that high-quality immunoassays for MPO and PR3 antibodies should be used as the primary screening method for patients suspected of having the ANCA-associated vaculitides GPA and MPA without the need for indirect immunofluorescence (IIF).4 It is worth noting that while MPO levels often decline following successful treatment of MPA, specific guidelines for this clinical purpose are not available.
Test results can not only expedite diagnosis but can also help rule out other possible diseases. For example, studies have shown that Autoimmune Thyroid Diseases (AITDs) are frequent exogenous triggers of ANCA-associated autoimmune diseases.6 Being able to quickly and correctly identify ANCA-associated vasculitis can mean the difference in the treatments chosen, unnecessary referrals, inappropriate therapies and the success of a patient’s outcome.