Diagnostic values of C-reactive protein and complete blood cell to identify invasive bacterial infection in young febrile infants

Background: Newborn infants younger than 3 months old with a fever are frequently evaluated for the risk of invasive bacterial infections (IBIs), which include bacteremia and/or bacterial meningitis, in the pediatric emergency department (PED). The purpose of this study was to determine the individual complete blood cell count and biochemistry levels associated with IBIs in febrile infants. Methods: We carried out this retrospective study using a pediatric emergency department at a tertiary medical center in southern Taiwan, where we also evaluated the clinical characteristics and routine blood tests between experimental groups. Results: We enrolled 1231 febrile infants under the age of 3 months old in this study. We found higher body temperature, neutrophil percentage, and C-Reactive protein (CRP) values and a lower hemoglobin level in the IBIs group. Furthermore, a CRP value greater than 25 mg/L can predict IBIs at a better rate than the group with values lower than 25 mg/L (11.7% vs. 2.1%, Odds ratio 6.3, p < 0.001). Conclusion: This study provides evidence that a CRP level greater than 25 mg/L can more accurately predict IBIs in febrile infants. Furthermore, lower hemoglobin levels were also found in IBIs. Nevertheless, additional laboratory tests are needed to identify young febrile infants with IBIs. Key Words: CRP, hemoglobin, invasive bacterial infection, young febrile infan