Original ArticleNew criteria for the diagnosis of infective endocarditis using 18F-FDG PET/CT imaging
Introduction
Infective endocarditis (IE) is defined as infection of a native or prosthetic heart valve (PVE) or an indwelling cardiac device (CIED).1 IE is associated with high-cost prolonged hospitalization and impaired quality of life.2
IE was described for the first time in 1885 by Osler, since then notable improvements in diagnosis and treatment have been made. However, the mortality is still high, about 20% in the first 30 days.3
The diagnosis of IE is based on the combination of clinical, laboratory, and imaging findings. Clinical and echocardiographic findings are non-specific especially in PVE and CIED. According to the latest update of the European Society of Cardiology (ESC) guidelines for the management of IE, 18-fluorine-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is included in the diagnostic flowchart for the diagnosis of IE especially in patients with prosthetic heart valve.4
In this context, the use of a simple qualitative criterion with good interpreter reliability, easy reproducibility, and good diagnostic performance would be crucial in the diagnosis. We propose a 4-point score, like Deauville score, to estimate the accuracy of 18F-FDG PET/CT in detecting IE. (The Deauville 5-point scoring system is an internationally accepted and utilized five-point scoring system for FDG avidity in patients with Hodgkin’s lymphoma or Non-Hodgkin’s lymphoma; scores of 1 and 2 are negative and 4 and 5 are considered to be positive)
We also evaluated a semi-quantitative criterion based on indirect signs such as a diffuse increase in spleen and/or bone marrow (BM) uptake. The host defense against IE involves the activation of polymorphonuclear cells, macrophages, and lymphocytes leading to an increase in the glycolytic metabolism, which could be documented in BM and spleen.5,6
The aim of our study was to examine the value of these 18F-FDG PET/CT methods in the diagnosis of IE.
Section snippets
Patients’ Selection and Preparation
We retrospectively included 108 patients (57males, 51 females, mean age 62 years; 25 with NVE and 83 with PVE and/or CIED) among patients who underwent 18F-FDG PET/CT scans from 2016 to 2020 for suspicious IE (Table 1).
All patients adopted a specific preparation consisting of a low-carbohydrate, high-protein, and high-fat diet (LCHPHF) protocol started 72 hours before the examination to reduce the high physiological myocardial FDG uptake. The LCHPHF diet was written in a menu of permitted and
Results
Of the 108 patients enrolled in the study, 54 (50%) had a final diagnosis of IE of which 19 (35%) had histopathology diagnosis, 14 (25%) had a diagnosis of IE confirmed by imaging, and 21 (38%) had a diagnosis confirmed by clinical follow-up and treatment response.
Comparing the score results with the final clinical diagnosis, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of our qualitative score were 93% [95% confidence interval (CI) 83%–98%],
Discussion
The key role of 18F-FDG PET/CT plays in diagnosis of IE is well established, especially in the “possible” cases according to Duke’s echocardiographic criteria, in PVE and CIED.
18F-FDG PET examinations performed in patients with known or suspected IE are influenced by several interfering factors: first, a physiological myocardial uptake of FDG, which could be avoided by an adequate diet preparation; and secondly the possible effect of antibiotics which could mask a correct diagnosis. For this
Conclusion
The proposed 4-point scale criteria are a simple, qualitative method with substantial inter-interpreter agreement and high positive predictive value and accuracy and may have a significant impact in the diagnosis of IE with PET/CT.
The HSBM is an additional, reliable indirect sign of IE and could strengthen the suspicion of IE, especially in the absence of any other infections, inflammatory or malignant disease.
These criteria could be useful for evaluating treatment response.
Limitations of the Study
This is a single center study with small number of patients, and thus further large multicenter and prospective studies are needed.
New Knowledge Gained
Combination of direct PET/CT interpretation criteria and indirect criteria leads to more reliable imaging methods using FDG/CT in the diagnosis of IE.
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A correction to this article is available online at https://doi.org/10.1007/s12350-022-02919-4.