Assessment of end organ damage in ANCA associated vasculitis

Assessment of organ involvement

• urinalysis is a sensitive means of detecting renal involvement, and an active urinary sediment with red blood cells (RBC) and casts indicates glomerular disease
  • serum urea and creatinine may be normal despite active renal disease
  • renal biopsy will serve to confirm the diagnosis and document the extent of renal inflammation or scarring
  • urinalysis is the single most important investigation. The extent of renal impairment and rate of deterioration in renal function is a major determinant of prognosis. The detection of proteinuria and/or haematuria in a patient with a systemic illness mandates immediate further investigation and is a medical emergency
    
    
• full blood count, ESR, CRP
  • leucocytosis suggests either a primary vasculitis or infection
  • leucopenia is a rare presenting feature of vasculitis and if present suggests vasculitis secondary to systemic lupus erythematosus or the effects of previous immunosuppressive therapy
  • a significant peripheral blood eosinophilia (1.5 x 109/l) suggests EGPA (Churg-Strauss) or a drug reaction
  • a hypochromic microcytic anaemia may be indicative of gastrointestinal bleeding, pulmonary haemorrhage or active persistent inflammation
  • degree of inflammation may be assessed by measurement of the acute phase response (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)). Neither is specific and each may be elevated in any inflammatory condition, including vasculitis
    • disproportionate increase in CRP compared with ESR should raise the suspicion of infection
      
      
• chest x-ray
  • should be performed in all patients with suspected systemic vasculitis to assess the presence of infiltrates, haemorrhage or granulomata and to exclude infection
    
    
• high-resolution computerised tomography (CT)
  • improves the detection of pulmonary lesions of GPA and pulmonary fibrosis, and can be useful in assessing response to treatment. Infection (especially tuberculosis), sarcoidosis and malignancy can mimic the CT appearance of GPA. Suspicious lesions should be biopsied to exclude malignancy or infection.
  • magnetic resonance imaging (MRI) or CT should be obtained to assess the extent of sinus involvement; however there is difficulty in distinguishing scarring from active disease
    
    
• patients with active ear, nose and throat (ENT) symptoms should have formal endoscopy by an otolaryngologist and biopsies obtained from areas of inflammation
  • Histology in active disease is often non-specific and is difficult to distinguish from chronic infection
    
    
• echocardiography is essential as part of the investigation to exclude bacterial endocarditis and atrial myxoma
  • Myocarditis is especially frequent in Churg Strauss and poor ventricular function can be demonstrated by echocardiography
    
    
• neurological signs may be subtle with evidence only of minor sensory impairment. Comprehensive nerve conduction studies are required to demonstrate evidence of mononeuritis multiplex

Reference:

1. Grayson PC et al. DCVAS Study Group. 2022 American College of Rheumatology/European Alliance of Associations for Rheumatology Classification Criteria for Eosinophilic Granulomatosis with Polyangiitis. Ann Rheum Dis. 2022 Mar;81(3):309-314.