Investigations for IgA vasculitis
The diagnosis of IgA vasculitis relies on the identification of typical clinical features and results of supportive investigations. There is no diagnostic test for IgA vasculitis. The diagnostic work up aims to exclude potential differential diagnoses, such as other small-vessel vasculitides (eg antineutrophil cytoplasmic antibodies (ANCA)–associated vasculitides), septicaemia, immune thrombocytopenic purpura, coagulation abnormalities, disseminated intravascular coagulation, thrombotic thrombocytopenic purpura and leukaemia.
Investigations may include:
- kidney work up—serum creatinine concentration, urinalysis (looking for haematuria) and urine protein to creatinine ratio
- inflammatory markers—erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) concentration
- full blood count
- anaemia due to gastrointestinal blood loss
- white cell count may be raised
- platelet count is usually normal or increased; important to exclude thrombocytopenia as a cause for purpura
- coagulation studies—usually normal; important to exclude coagulopathy as a cause for purpura
- skin biopsy (not specifically required)—may be considered if atypical rash is present to look for IgA immune-complex deposition; however, absence of IgA immune-complex deposition does not exclude IgA vasculitis
- abdominal ultrasound—if intussusception is considered (a complication of IgA vasculitis)
- antinuclear antibodies (ANA) and antineutrophil cytoplasmic antibodies (ANCA)—usually not required unless there is a strong suspicion of a systemic inflammatory connective tissue disease
- kidney biopsy—if severe or persistent proteinuria, or kidney impairment.