Abstract: Objectives To evaluate the clinical utility of systematic serological testing in infective endocarditis (IE), determine the prevalence of blood-culture negative IE (BCNIE), and characterize its clinical presentation in our cohort. Methods Retrospective analysis of 296 consecutive IE episodes (2008-2021) at a tertiary hospital. We compared clinical characteristics, serological testing patterns, and outcomes between BCNIE and blood-culture-positive IE (BCPIE) cases. Results BCNIE accounted for 22.3% (66/296) of cases. Prior antibiotic use was significantly higher in BCNIE (27.3% vs 2.2%, P < 0.001). Serological testing was performed in 81.8% of BCNIE and 71.3% of BCPIE cases. Despite positive serological results for Coxiella burnetii phase I IgG (24.2% of tested cases), Bartonella henselae IgG (14.9%), Mycoplasma pneumoniae IgM (6.9%), and Brucella spp. (1.5%), only one patient (1.9% of all positive results) received targeted antimicrobial therapy. In multivariate analysis, no serological marker was associated with improved clinical outcomes. Conclusions Systematic serological testing in IE provides limited diagnostic and therapeutic value. A selective approach targeting BCNIE cases with specific epidemiological risk factors appears more appropriate and cost-effective.
