C-Reactive Protein, Interleukin-6, and Procalcitonin in Diagnosis of Late-Onset Bloodstream Infection in Very Preterm Infants

Abstract

Abstract Background Late-onset bloodstream infection (LOBSI) is common in very preterm infants. Early and accurate diagnosis is crucial for prognosis and outcome. We aimed to analyze the accuracy of routinely used inflammatory biomarkers in the diagnosis of LOBSI as compared to uninfected controls. Methods In this single-center, retrospective case-control study, interleukin-6 (IL-6), procalcitonin (PCT), and C-reactive protein (CRP) were routinely measured, when infection was clinically suspected. The definition of LOBSI was based on positive blood culture, clinical signs of infection, and onset more than 72 hours after birth. Results Among 285 enrolled infants, 66 developed LOBSI. IL-6 was superior to other markers, and levels greater than 100 ng/L had a sensitivity of 94% and a specificity of 99% for the presence of LOBSI. Receiver operating characteristic curve of IL-6 had area under the curve of 0.988 (95% CI = 0.975-1.00, P < .001). The negative predictive value of IL-6, CRP, and PCT for optimal cutoff values was 99%, 95%, and 93%, respectively. The logistic regression model of IL-6 > 100 ng/L or CRP > 10 mg/L were successfully predicted LOBSI in 97.9% of cases. Conclusions The combination of IL-6 and CRP seems to have great potential in routine rapid diagnosis of LOBSI development. High negative predictive value of all tested markers could encourage the early discontinuation of antibiotic treatment.