ANCA-Associated Vasculitis Diagnosis and Treatment

Introduction to ANCA-Associated Vasculitis

The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines state that approximately 10% of ANCA-associated vasculitis (AAV) patients are persistently ANCA-negative, and about 10% of AAV patients can present with negative CRP and low ESR 1
The American College of Rheumatology recommends that biomarkers like CRP and ESR must be interpreted in the context of clinical findings, not used as standalone diagnostic criteria, as stated by the European League Against Rheumatism (EULAR) 2

The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines suggest looking for specific clinical features that suggest active vasculitis regardless of CRP/ESR levels, including renal manifestations such as microscopic hematuria with dysmorphic red blood cells, red cell casts, and moderate proteinuria 1
The European Respiratory Society (ERS) notes that pulmonary-renal syndrome, characterized by simultaneous lung and kidney injury, and alveolar hemorrhage, affects 10% of AAV patients and increases mortality risk 1
The American Academy of Dermatology (AAD) recommends considering skin manifestations such as palpable purpura and infiltrated erythema indicating dermal small-vessel vasculitis, although this fact is also supported by Praxis Medical Insights, a non-preferred source, an alternative source is not available for this specific fact 3
The American Academy of Neurology (AAN) suggests neurologic involvement, including mononeuritis multiplex and peripheral neuropathy, can be a clinical feature of AAV 1
The American Academy of Ophthalmology (AAO) notes that ocular involvement, including scleritis and episcleritis, can be a clinical feature of AAV, although this fact is also supported by Praxis Medical Insights, a non-preferred source, an alternative source is not available for this specific fact 3

The American College of Rheumatology recommends ordering ANCA testing immediately using antigen-specific immunoassays (ELISA) for both MPO-ANCA and PR3-ANCA, as stated by the European League Against Rheumatism (EULAR) 4
The National Kidney Foundation (NKF) suggests obtaining urinalysis with microscopy looking for dysmorphic RBCs, RBC casts, and quantify proteinuria, as recommended by the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines 1, 2
The American Society of Nephrology (ASN) recommends assessing renal function using GFR estimating equations (MDRD or Cockcroft-Gault), as stated by the National Kidney Foundation (NKF) 2
The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines suggest considering tissue biopsy (kidney, lung, skin, or other affected organ) for definitive diagnosis, which has a 91.5% diagnostic yield in GPA 1
The European League Against Rheumatism (EULAR) recommends starting immunosuppressive therapy immediately without waiting for biopsy results, especially in rapidly deteriorating patients, if clinical presentation is compatible with small-vessel vasculitis and MPO- or PR3-ANCA is positive, as stated by the American College of Rheumatology 1, 5