Serum PCT level was significantly higher in patients with infections (0.98 ± 0.12 μg/L) than in those with viral infections (0.13 ± 0.04 μg/L), SLE flare (0.24 ± 0.18 μg/L), or controls (0.12 ± 0.03 μg/L) [12]. Here, CALCA is linked to viral infectious disease.