The median PCT level was significantly higher in patients with bacterial infection than in those without infection through days 0 to 5 of fever (P < 0.05), but there was no significant difference at 7 days of fever (median ng/dL (IQR), 0.17 (0.16 ~ 0.38) versus 0.15 (0.12–0.93), P = 0.556). Here, CALCA is linked to bacterial infectious disease.