Clinical value of serum procalcitonin in diagnosis of sepsis caused by gram negative bacterial infection

Objective To investigate the correlation between serum procalcitonin (PCT) levels and infection sites, as well as between PCT and bacterial species in gram negative (G-) bacteria induced sepsis, so as to provide rationale for therapeutic strategy of using antibiotic in sepsis. Methods The data of patients with sepsis admitted in Emergency Department and ICU from January 2014 to June 2015 were retrospectively analyzed. The blood culture of G- bacteria and PCT detection were carried out simultaneously within 24 hours after admission. The clinical data was analyzed to find out the correlation between PCT levels and infection sites, as well as between PCT levels and pathogenic bacterial species. Results A total of 187 specimens (came from 162 patients) were enrolled in the study with a median age of 70 years old and a median sequential organ failure assessment (SOFA) score of 4. PCT levels were found to be associated with bacterial species. PCT level caused by Escherichia coli bacteremia infection was higher than that caused by Acinetobacter baumannii bacteremia and Burkholderia cepacia bacteremia infection(4.62 ng/mL vs. 2.44 ng/mL; 4.62 ng/mL vs. 0.81 ng/mL; P<0.05). Receiver operating characteristic (ROC) analysis showed an area under the curve (AUC) for PCT was 0.61 to discriminate Escherichia coli infection from Acinetobacter baumannii infection and an AUC was 0.66 to discriminate Escherichia coli infection from Burkholderia cepacia infection. When the cutoff point of PCT was 30.32 ng/mL, it could predict Escherichia coli infection rather than Acinetobacter baumannii infection with 94.10% specificity, 90.00% positive predictive value and positive likelihood ratio for 4.24. When the cutoff point of PCT was 8.01 ng/mL, it could predict Escherichia coli infection rather than Burkholderia cepacia infection with 85.70% specificity, 93.94% positive predictive value, and positive likelihood ratio for 3.01. When PCT cutoff value reached 47.31 ng/mL, the specificity and positive predictive value were both 100.00%. PCT level caused by urinary tract infection was higher than that caused by pulmonary infection(11.58 ng/mL vs. 2.07 ng/mL, P<0.05), and the AUC was 0.69. When the cutoff point of PCT was 32.11 ng/mL, it could predict Escherichia coli infection rather than Acinetobacter baumannii infection with 90.60% specificity, 86.18% negative predictive value and positive likelihood ratio for 3.68. Conclusions PCT elevation in G- bacteria induced sepsis might be associated with infection sites and bacterial species. Key words: Procalcitonin; Gram negative bacteria; Infection sites; Bacterial species; Sepsis