Assessment of disease activity in Takayasu's arteritis

Takayasu's arteritis (TA) is a large vessel vasculitis of unknown etiology, more common among Asians. Since it is a smoldering, chronic disease, assessment of disease activity is a challenge. Acute phase reactants, erythrocyte sedimentation rate and CRP, imperfectly correlate with disease activity on histopathology. The earliest clinical criteria to assess disease activity were the NIH criteria, taking a composite of clinical features, inflammatory markers, and imaging to assess disease activity in TA. Of late, clinical scoring systems like DEI.Tak (Disease Extent Index in TA), derived from the BVAS scoring for small vessel vasculitis, and the ITAS2010 and ITAS-A, derived from DEI.Tak, have been validated. Serum biomarkers like matrix metalloproteinases 2, 3, and 9, pentraxin-3 and soluble receptor for advanced glycation end products hold promise in assessing disease activity. Recently, endothelial microparticles have been shown to correlate with active TA. Evidence suggests wall edema, and contrast uptake in the vessel wall on angiography may suggest active TA. Scoring systems assessing angiographic extent of TA are a work in progress, validation of which shall help quantify extent of vascular involvement in TA, and serial follow-up might prove valuable for assessment of disease activity. PET-CT is useful to diagnose prepulseless TA; however, its utility in patients on immunosuppression is debatable. Analysis of serum metabolites using nuclear magnetic resonance spectroscopy is a promising exploratory approach towards identifying new biomarkers in TA. There remains an unmet need for a composite index, taking into account clinical features, serial radiography, and circulating biomarkers, to assess disease activity in TA.