Investigations in systemic vasculitis. The role of the laboratory.

Abstract

The diagnosis of systemic vasculitis is challenging. Laboratory testing may provide useful information. Routine laboratory tests include erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), blood count, serum creatinine, urinalysis, specific autoantibodies, complement, immunoglobulin, cryoglobulin, and Hepatitis B and C serology. Although ESR and CRP are often helpful for the diagnosis of vasculitis, they are nonspecific and do not help in distinguishing between vasculitis disease activity and a concomitant infection or another source of inflammation. A few autoantibodies are helpful for diagnosis, such as anti-neutrophil cytoplasmic antibodies (ANCAs) (in ANCA-associated small-vessel vasculitis), anti-glomerular basement membrane (GBM) antibodies (in anti-GBM antibody disease), and anti-C1q antibodies (in immune complex-associated small-vessel vasculitis). The 2017 revised consensus recommendations on ANCA testing state that high-quality antigen-specific immunoassays are the preferred screening methodology for the diagnosis of ANCA-associated vasculitis. ANCA subtypes (proteinase-3-ANCA and myeloperoxidase-ANCA) are associated with different epidemiological, genetic, and clinical features.