What investigation should be ordered to assess a child with Anti-Neutrophil Cytoplasmic Antibodies (ANCA) vasculitis?

From the Guidelines

For a child with suspected ANCA vasculitis, I strongly recommend ordering a comprehensive panel of investigations, including ANCA testing with both immunofluorescence patterns and ELISA for specific antigens, as the primary method of testing, as stated in the 2022 EULAR recommendations 1. This approach is crucial for confirming the diagnosis, assessing disease severity, and evaluating organ involvement. The initial testing should include:

• A complete blood count to check for anemia, leukocytosis, and thrombocytosis
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to assess inflammation
• A comprehensive metabolic panel to evaluate kidney and liver function
• Specific autoimmune markers, such as ANCA testing with both immunofluorescence patterns (c-ANCA and p-ANCA) and ELISA for specific antigens (PR3-ANCA and MPO-ANCA), as recommended in the EULAR guidelines 1
• Urinalysis with microscopy to detect hematuria, proteinuria, and cellular casts
• A 24-hour urine collection to quantify protein excretion and creatinine clearance
• Complement levels (C3, C4) and anti-GBM antibodies to rule out Goodpasture's syndrome Imaging studies, such as chest X-ray and possibly chest CT, should be performed to detect pulmonary involvement, and renal ultrasound to assess kidney structure. In cases with renal involvement, a kidney biopsy may be necessary to confirm the diagnosis and determine the extent of damage, as suggested by the EULAR recommendations 1. Pulmonary function tests and bronchoscopy with bronchoalveolar lavage may be indicated if respiratory symptoms are present. These investigations are crucial for establishing the diagnosis, determining disease subtype, assessing organ damage, and guiding appropriate treatment decisions in pediatric ANCA vasculitis, in line with the EULAR guidelines 1 and other evidence-based recommendations 1.

From the Research

Investigations for ANCA Vasculitis

To assess a kid with ANCA vasculitis, the following investigations can be ordered:

• Routine laboratory tests, including:
  • Erythrocyte sedimentation rate (ESR) 2
  • C-reactive protein (CRP) 2
  • Blood count 2
  • Serum creatinine 2
  • Urinalysis 2, 3
• Specific autoantibodies, including:
  • Anti-neutrophil cytoplasmic antibodies (ANCAs) 2, 4, 5, 6
  • ANCA subtypes (proteinase-3-ANCA and myeloperoxidase-ANCA) 2, 4, 6
• Other tests, including:
  • Complement 2
  • Immunoglobulin 2
  • Cryoglobulin 2
  • Hepatitis B and C serology 2
  • Tissue biopsy may be necessary for confirmation of the diagnosis 5

Urinalysis

Urinalysis can be useful in determining the risk of renal relapse in ANCA-associated vasculitis, with persistent hematuria being a significant predictor of future renal relapse 3.

ANCA Testing

High-quality antigen-specific immunoassays are the preferred screening methodology for the diagnosis of ANCA-associated vasculitis 2. ANCA testing can help guide diagnosis and treatment decisions, and patients should be frequently evaluated during follow-up for possible disease relapses or treatment-related morbidity 5.