Illuminating the Challenges and Diagnostic Utility of Plasma Microbial Cell-Free DNA Sequencing in Suspected Infective Endocarditis: A Retrospective Observational Cohort Study.

Background: Infective endocarditis (IE) is a life-threatening infection often challenging to diagnose, particularly in culture-negative cases. Plasma microbial cell-free DNA (mcfDNA) sequencing has shown potential for detecting pathogens in IE. However, its clinical utility, diagnostic impact, and limitations remain debated. This study evaluates its use in diagnosing and managing IE in a tertiary care setting. Methods: This single-center retrospective cohort study included adult patients (≥18 years) who underwent mcfDNA sequencing via the Karius test for suspected IE at Mayo Clinic Rochester between December 2019 and February 2024. Diagnostic classification followed the 2023 Duke-International Society of Cardiovascular Infectious Diseases criteria. Data on demographics, clinical features, routine microbiologic workup, and mcfDNA sequencing results were collected. Statistical analysis was conducted to evaluate diagnostic utility and treatment impact. Results: Among 141 patients, 66 had a diagnosis of IE, with mcfDNA sequencing identifying pathogens in 60.6% of them, compared with 39.4% with routine workup. mcfDNA sequencing was the sole microbiologic test with positive results in 33.3% of patients, leading to antimicrobial adjustments in 50.0% of that group. Clinically insignificant mcfDNA sequence detection occurred in 28.6% of patients without a diagnosis of IE. Conclusions: mcfDNA sequencing is a valuable adjunctive tool for diagnosing culture-negative IE and guiding antimicrobial therapy when clinical suspicion is high. However, its utility depends on appropriate clinical context, highlighting the need for careful test interpretation and further prospective studies to assess patient-centered outcomes and cost-effectiveness.