Blood Biomarkers for Monitoring and Prognosis of Large Vessel Vasculitides.

Large vessel vasculitides (LVVs) are inflammatory conditions of the wall of large-sized arteries, mainly represented by giant cell arteritis (GCA) and Takayasu arteritis (TA). The inflammatory process within the vessel wall can lead to serious consequences such as development of aneurysms, strokes and blindness; therefore, early diagnosis and follow-up of LVV are fundamental. However, the arterial wall is poorly accessible and blood biomarkers are intended to help physicians not only in disease diagnosis but also in monitoring and defining the prognosis of these conditions, thus assisting therapeutic decisions and favouring personalised management. The field is the object of intense research as the identification of reliable biomarkers is likely to shed light on the mechanisms of disease progression and arterial remodelling. In this review, we will discuss the role of blood biomarkers in LVVs in the light of the latest evidence. In clinical practice, the most widely performed laboratory investigations are the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). However, these indices may be within normal limits during disease relapse and they are not reliable in patients receiving interleukin-6 (IL-6) receptor inhibitors. New biomarkers struggle to gain traction in clinical practice and no molecule with good accuracy has been identified to date. IL-6, a pro-inflammatory cytokine that drives CRP synthesis and increases the ESR, is one of the most promising biomarkers in the field. IL-6 analysis is increasingly performed, and serum levels are more sensitive than ESR for active GCA and might reflect persistent inflammation with high risk of relapse in patients on IL-6 receptor inhibitors. A future with biomarkers that reflect different disease features is an important aspiration. Accordingly, intense effort is being made to identify IL-6-independent inflammatory biomarkers, such as S100 proteins, pentraxin-3 and osteopontin. Moreover, metalloproteinases such as MMP2/9 and angiogenic modulators such as VEGF, YLK-40 and angiopoietins are being studied as markers of arterial remodelling. Lastly, biomarkers indicating organ damage may guide prognostic stratification as well as emergency therapeutic decisions: the most promising biomarkers so far identified are NT-proBNP, which reflects myocardial strain; pentraxin-3, which has been associated with recent optic nerve ischemia; and endothelin-1, which is associated with ischaemic complications. Currently, the use of these molecules in clinical practice is limited because of their restricted availability, lack of sufficient studies supporting their validity and associated costs. Further evidence is required to better interpret their biological and clinical value.