CIRP was strongly linked to the major/minor criteria, SOFA and PSI scores, mortality, PCT, IL-6 and CRP, had a significant increased OR for mortality, and best predicted mortality, indicating that it might determine the severity of CAP and the presences of IDSA/ATS major/minor criteria and suggesting that it might be a novel and intriguing biomarker for pneumonia to monitor host response and predict mortality. The gene discussed is CRP; the disease is pneumonia.