Impact of Viral Illness on Procalcitonin as a Predictor of Bacterial Infection in Febrile Infants

Abstract

Objective:The impact of confirmed viral infections (CVI) on procalcitonin (PCT) levels in febrile infants aged 8-60 days with a bacterial illness (BI) is unknown. The objectives of the study were: (1) examine association of CVI with PCT levels in patients with and without a concurrent BI, defined as bacteremia, meningitis, or urinary tract infection, and (2) assess PCT as a predictor of BI in infants with a concurrent CVI. Methods:A single center, retrospective cohort study examined febrile infants aged 8-60 days presenting between 1/2018-12/2020. PCT was compared between groups, according to results of bacterial cultures and viral tests, using the Wilcoxon rank sum test. Prediction ability of PCT to detect BI with/without concurrent CVI was assessed via area under the curve from logistic regression. Results:Patients included: 404 BI-/CVI+, 73 BI+/CVI-, 48 BI+/CVI+, and 138 BI-/CVI-. Median PCT level in the BI+/CVI+ group was significantly lower when compared to BI+/CVI- (0.36ng/mL vs 0.89ng/mL), but significantly higher than the BI-/CVI- group (0.36ng/mL vs 0.1ng/mL). The presence of a CVI reduced the sensitivity of procalcitonin in BI detection (68% vs. 44%), with minimal impact on specificity (93% vs. 96%). Conclusion:In previously healthy febrile infants 8-60 days old, the presence of a CVI reduces the sensitivity of PCT in detection of a BI without impacting its specificity. The impact of a CVI on PCT levels in febrile infants has implications for how this marker of infection should be considered when assessing risk of BI in infants.