CALCA and bacterial infectious disease: C-reactive protein is a marker of inflammation and its levels increase during bacterial infection.[43] Some studies have found that there is a correlation between elevated interleukin-6 levels and elevated C-reactive protein levels when inflammation occurs in the body, which may be because interleukin-6 can induce the C-reactive protein gene.[44] Procalcitonin is a 116 amino acid prohormone of calcitonin.