Abstract
AIM: The aim of this study is to investigate the utility of interleukin-6 (IL-6) in the early diagnosis of serious bacterial infections (SBI) in febrile infants and to compare it with C-reactive protein (CRP). METHODS: Retrospective study conducted in the paediatric emergency department in Gothenburg, Sweden, on previously healthy, full-term infants aged ≤60 days with fever without a source (FWS) from 2014 to 2017. RESULTS: We included 536 infants with FWS, of whom IL-6 was analysed in 364 (68%) and CRP was analysed in 494 (92%). Approximately 70% of the infants presented with a fever duration of less than 12 h. The prevalence of SBIs was 14.8% (95% CI,11.3-18.9) in the IL-6 group and 17.8% (95% CI,14.5-21.5) in the CRP group. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of IL-6 ≥50 ng/L were 93%, 66%, 98% and 33%, respectively. For CRP ≥20 mg/L, the sensitivity, specificity, NPV, and PPV were 76%, 89%, 95%, and 55%, respectively. Logistic regression analysis showed that CRP was significantly associated with SBI (p < 0.0001) in the entire population, whereas IL-6 was not. CONCLUSION: Interleukin-6 showed high sensitivity and NPV, which might assist in identifying SBIs early in febrile infants. However, IL-6 was not shown to be superior to CRP and further studies are needed to investigate whether IL-6 should be incorporated in clinical management.