Validation of the VIRSTA and VIRSTA+ Scores to Identify Patients with Staphylococcus aureus Bacteremia at Very Low Risk of Infective Endocarditis

INTRODUCTION: Adherence to guideline recommendations on the use of echocardiography in all patients with Staphylococcus aureus bacteremia (SAB) is heterogeneous. This study aims to validate the VIRSTA and VIRSTA+ scores as tools for risk stratification to identify patients at low risk of infective endocarditis (IE) and support the prioritization of transthoracic echocardiography (TTE). METHODS: This is a retrospective analysis of a prospectively assembled cohort of adult patients with SAB admitted between January 2006 and December 2022. Patients who did not undergo an echocardiogram were excluded, as well as those who died within the first 48 h, those receiving antibiotic treatment during blood culture collection, and individuals without recorded time to positivity (TTP). VIRSTA and VIRSTA+ scores were calculated from clinical records, and their diagnostic performance was assessed. IE diagnosis, defined using modified Duke criteria, was compared between patients classified as low and high risk according to these scores. RESULTS: Of a total of 1668 episodes diagnosed with SAB, 798 adult patients were included in the final analysis. Median (interquartile range [IQR]) TTP was 8 (7-11) h for IE cases and 12 (9-15) h for non-IE cases. In VIRSTA ≥ 3 episodes, IE was observed in 108 (19%) patients, compared with 1/238 (0.4%) with VIRSTA < 3 corresponding to a sensitivity of 99%, a specificity of 34.4% with a positive predictive value of 19.3%, and a negative predictive value (NPV) of 99.5%. The single patient with IE and a VIRSTA < 3 had a TTP < 11.5 h. Accordingly, the NPV of VIRSTA+ achieved 100%. CONCLUSIONS: VIRSTA and VIRSTA+ demonstrated high NPV for risk stratification in SAB, suggesting that they could help prioritize procedures and guide decision-making in clinical practice, particularly in resource-constrained settings.