It is widely accepted that 0.25 ng/mL for PCT is the cut-off value for lower respiratory tract infections in the general population,[20–21] so when using 0.25 ng/mL to identify infectious complications in patients with chronic liver disease (Table 5), the diagnostic sensitivity improved but the specificity decreased significantly, and thus the diagnostic efficiency also decreased. The gene discussed is CALCA; the disease is Recurrent lower respiratory tract infections.