Here, the isolated AH1N1 (n = 84) was compared against a bacterial pneumonia group (consisting of 37 patients with isolated bacterial pneumonia and 40 with mixed bacterial/influenza infection; no subgroup analysis was performed); after excluding hospital-acquired cases and immunodeficient patients, and the PCT’s NPV was 0.822 (at a cut-off of 0.5 ng/mL), which is closer to our outcomes. The gene discussed is CALCA; the disease is bacterial pneumonia.