Abstract: OBJECTIVE To analyze the application value of combined detection of procalcitonin (PCT), high sensitive C reactive protein (hs-CRP), white blood cell count (WBC) and neutrophil count (NEU) in bacterial infections in elderly patients with coronary heart disease. METHODS A total of 275 cases of elderly patients with coronary heart disease from Jan. 2014 to Dec. 2016 were selected as the research subjects. According to whether the infections occurred, they were divided into infection group (152 cases) and non-infection group (123 cases). The occurrence of bacterial infections during hospitalization of the patients were observed and recorded. The pathogens, infection situation, and PCT, hs-CRP, WBC and NEU levels of the patients with different infected sites were analyzed and compared, and the application value was investigated. RESULTS There were 152 cases that had infections, and the infection rate was 55.27%, which was mainly respiratory tract infections. Totally 273 strains of pathogens were detected, including 197 strains of gram-negative bacteria, accounting for 72.16% and mainly were Escherichia coli, and 76 strains of gram-positive bacteria, accounting for 27.84%, which were mainly Klebsiella pneumoniae. The blood indexes of the two groups had significant differences (P<0.05). The PCT and hs-CRP levels of patients with bloodstream infections were the highest, followed by patients with chest abdominal infections and patients with respiratory tract infections, and those of patients with urinary tract infections were the lowest. In such four blood indexes, AUC and Youden indexes of the serum PCT level in the diagnosis of the bacterial infections in elderly patients with coronary heart disease were the highest, which were respectively 0.861 and 0.603. When the combined detection of such four blood indexes was applied, AUC and Youden indexes in the diagnosis of the bacterial infections in elderly patients with coronary heart disease increased significantly, which were respectively 0.943 and 0.715. CONCLUSION The incidence of bacterial infections in elderly patients with coronary heart disease is high, the infected sites and the distribution of pathogens have certain characteristics. The application of combined detection of PCT, hs-CRP, WBC and NEU can be auxiliary tools in the diagnosis of bacterial infections in elderly patients with coronary heart disease.