CALCA and bacterial infectious disease: Therefore, the authors implemented an interventional PCT treatment algorithm incorporating the increasing risk of bacterial infection with increasing PCT values: PCT < 0.1 ng/mL: bacterial infection highly unlikely and antibiotic treatment strongly discouraged, PCT < 0.25 ng/mL: bacterial infection unlikely and antibiotic treatment rather discouraged, PCT ≥ 0.25 ng/mL: bacterial infection possible and start of antibiotic treatment advised, PCT ≥ 0.5 ng/mL: bacterial infection suggestive and antibiotic treatment strongly advised.