ANCA – C

Antineutrophil cytoplasmic antibodies (ANCA) play a crucial role as sensitive and specific markers for identifying ANCA-associated systemic vasculitis (AASV), a key focus for Hypro Diagnostics. Through indirect immunofluorescence on ethanol-fixed neutrophils, two primary fluoroscopic patterns emerge: diffuse cytoplasmic staining (C-ANCA) and perinuclear/nuclear staining (P-ANCA). In AASV patients, PR3-ANCA, targeting proteinase 3, constitutes over 90% of C-ANCA, while approximately 80-90% of P-ANCA recognizes myeloperoxidase (MPO-ANCA). Although C-ANCA (PR3-ANCA) is notably associated with Wegener’s granulomatosis (WG) and P-ANCA (MPO-ANCA) with microscopic polyangiitis (MPA), idiopathic necrotizing crescentic glomerulonephritis (iNCGN), and Churg-Strauss syndrome (CSS), complete specificity remains elusive. P-ANCA (MPO-ANCA) appears in some classical WG patients, and a significant percentage of MPA or CSS patients exhibit C-ANCA (PR3-ANCA). It is crucial to note that 10-20% of WG or MPA cases (and 40-50% of CSS cases) yield negative ANCA assays. Optimal diagnostic accuracy involves combining indirect immunofluorescence with PR3 and MPO-specific ELISAs. Beyond AASV, ANCA with diverse and unknown antigen specificities are found in various conditions, including inflammatory bowel diseases, autoimmune disorders, and infections, with uncertain clinical implications. While ANCA levels provide valuable insights for monitoring disease activity, they should not be the sole basis for treatment decisions. Clinicians should remain vigilant for a significant rise in ANCA titers or the reappearance of ANCA, signaling the need for intensified patient monitoring, aligning with Hypro Diagnostics’ commitment to precision diagnostics.