Blood Culture Negative Endocarditis; What Do Concurrent Cardiac Disorders Tell Us?

Purpose: Blood culture negative endocarditis (BCNE) presents diagnostic challenges, necessitating precise identification of high-risk patient cohorts. Hence, our objective was to pinpoint high-risk cohorts for BCNE. Methods: The study included adult patients with definite endocarditis. Data was collected via the Infectious Diseases International Research Initiative (ID-IRI). The primary study analysing one of the largest case series ever reported and was published in the European Journal of Clinical Microbiology and Infectious Diseases in 2019, was conducted across 41 centres in 13 countries. We performed a re-analysis of the database to determine the predictors of BCNE. Results: 867 cases with definite endocarditis were included in the study. Blood cultures were negative in 101 (11.65%) patients. We disclosed that as patients age, the likelihood of a negative blood culture significantly decreases (OR 0.975, 95% CI 0.963-0.987, p<0.001). Additionally, factors such as rheumatic heart disease (OR 2.036, 95% CI 0.970-4.276, p=0.049), aortic stenosis (OR 3.066, 95% CI 1.564-6.010, p=0.001), mitral regurgitation (OR 1.693, 95% CI 1.012-2.833, p=0.045), and prosthetic valves (OR 2.539, 95% CI 1.599-4.031, p<0.001) are associated with higher likelihoods of negative blood cultures. Our model can predict whether a patient falls into the culture-negative or culture-positive groups with a threshold of 0.104 (AUC±SE=0.707±0.027). The final model demonstrates a sensitivity of 70.3% and a specificity of 57.0%. Conclusion: Our study reveals a high prevalence of negative blood cultures in patients with concurrent cardiac disorders, particularly in younger cases. Therefore, caution is indicated in diagnosing and treating endocarditis in these particular patient subgroups.