Serology testing in pulmonary renal syndromes
| ANCA-associated vasculitis | |
| Granulomatosis with polyangiitis (GPA) | ANCA positive 90% [61]; PR3 positive in 75% |
| Microscopic polyangiitis (MPA) | ANCA positive 60% [61]; MPO positive in 65% |
| Eosinophilic granulomatosis with polyangiitis (EGPA) | ANCA positive 30–70% [61]; PR3 positive in 5%, MPO positive in 45% [62] |
| Anti-GBM disease | Anti-GBM antibodies are 95–100% sensitive and 90–100% specific [10, 63, 64] |
| ANCA-negative vasculitis | |
| IgA disease | Nil specific |
| Cryoglobulinaemia | Hepatitis serology; serum cryoglobulins [65] |
| Autoimmune connective tissue disease | |
| Systemic lupus erythematosus (SLE) | Anti-dsDNA, anti-Smith, anti-C1q antibodies |
| Antiphospholipid syndrome (APS) | Anti-cardiolipin, lupus anticoagulant antibodies |
| Rheumatoid arthritis (RA) | Rheumatoid factor, anti-cyclic citrullinated peptides |
| Mixed connective tissue disease (MCTD) | Anti-RNP |
| Polymyositis and dermatomyositis | Anti-Jo1, anti-Ro antibodies |
| Systemic sclerosis | Anti-centromere, anti-Scl70 [60, 66] |
Positive serology can aid in narrowing the diagnosis in pulmonary renal syndrome. Differentiating between ANCA-positive and ANCA-negative serology is often the first step in determining the cause. ANCA: anti-neutrophil cytoplasm antibodies; GBM: glomerular basement membrane; PR3: proteinase-3; MPO: myeloperoxidase; dsDNA: double-stranded DNA.