CALCA and rheumatoid arthritis: The levels of PCT in RA and AS patients were positively correlated with disease activity indices DAS28 (r = 0.08; p = 0.61) and ASDAS (r = 0.26; p = 0.10), CRP (r = 0.27; p = 0.10/ r = 0.48; p = 0.001) respectively, no significant correlation was observed in RA and AS patients (Figs 3–4), except CRP in AS (Fig 4B).