CALCA and rheumatoid arthritis: The serum levels of PCT in GA (0.41 ± 1.23, n = 51) is significantly higher when compared with RA (0.09 ± 0.12, n = 37) (p = 0.002), AS (0.09 ± 0.10, n = 41) (p = 0.0007) and HC (0.04 ± 0.02, n = 46) (p< 0.0001) (Fig 1A).