Usefulness of Procalcitonin in the Diagnosis of Bacterial Infection in Immunocompetent Children

Bacterial infections (BIs) need to be differentiated from non-BIs (NBIs) to enable prompt administration of antibiotics. Therefore, inflammatory biomarkers are needed as they can accurately identify BIs. This study evaluated the usefulness of procalcitonin (PCT) in the diagnosis of BI in immunocompetent children. We retrospectively reviewed the medical records of patients <18 years who underwent PCT measurements between July 2012 and June 2019. In total, 474 patients were enrolled and divided into the BI (n = 205) and NBI groups (n = 269). The BI group was subcategorized into the invasive BI (IBI; n = 94), mucosal BI (MBI; n = 31), toxigenic BI (TBI; n = 23), and localized BI (LBI; n = 57) subgroups. The NBI group was further subcategorized into the viral infection (VI; n = 118) and inflammatory disease groups (ID; n = 151). PCT was compared with the levels of C-reactive protein (CRP), white blood cell (WBC), and erythrocyte sedimentation rate (ESR). Between the BI and NBI groups, PCT (4.2 ± 16.9 vs. 1.1 ± 2.5 ng/mL; p = 0.008) and ESR (39.1 ± 32.4 vs. 54.8 ± 28.2 mm/h; p < 0.001) were significantly different. Between the IBI and other groups, WBC (14,797 ± 7148 vs. 12,622 ± 5770 × 10(6)/L; p = 0.007), ESR (35.3 ± 30.3 vs. 51.5 ± 30.3 mm/h; p < 0.001), and PCT (8.1 ± 23.8 vs. 1.0 ± 3.4 ng/mL; p = 0.005) were significantly different. However, none of the biomarkers were useful in differentiating BI from NBI. While WBC (area under curve (AUC) = 0.615, p = 0.003) and PCT (AUC = 0.640, p < 0.001) were useful, they fared poorly in differentiating IBI from other groups. Thus, additional studies are needed to identify more accurate biomarkers capable of differentiating BIs, especially IBIs.