Ankylosing Spondylitis (AS) is a common cause of chronic inflammatory arthritisworldwide, with a prevalence of 0.2-0.9% in white European populations (Braun et al., 1998),with unknown etiology. The progressive ankylosis of affected joints is currently irreversible and it is, therefore, logical that early diagnosis and treatment offers the best opportunity to improve its prognosis. Several studies have shown a delay of more than 8 years between the onset of symptoms and diagnosis, with consequent delay in starting an effective therapy (Feldtkeller et al., 2003; Hamilton et al., 2011). This is a critical period clinically, with diagnosis frequently occurring after significant irreversible radiological damage has already occurred. Currently, diagnosis of AS relies on a combination of clinical and imaging parameters (van der Linden et al., 1984 and Boonen et al., 2010) with no single blood derived biomarker that by itself is sufficiently sensitive and specific to identify AS cases or to be useful in disease management.