Infective endocarditis (IE): 18F-FDG PET

Purpose: The clinical course of IE varies from uncomplicated disease to fulminant infection. Despite we are witnessing a significant and progressive increase in its incidence, many difficulties in early diagnosis haven’t been overwhelmed yet. New diagnostic criteria are, therefore, necessary. FDG PET/CT is an imaging procedure that is being considered as a possible tool to increase the accuracy in IE diagnosis. The serum level of C-reactive protein (CRP) is used as an indicator of an inflammatory status and is predictive of the clinical outcome. The aim of this study is to explore if CRP serum level could be correlated to the activity of the infection at FDG PET/CT (SUV max) and to assess if a CRP cut-off may be used to optimize the indication to FDG PET/CT, which is a high cost imaging procedure. Methods: 55 pts (19 f, 36 m) with prosthetic (28: 19 aortic;5 mitral, 4 mitral-aortic) or native (27) valve were enrolled by the clinical suspect of IE (echocardiography, Duke criteria, blood cultures, physical exam and serological markers of inflammation (CRP mg/dl on the day of PET/CT)). They underwent 18F-FDG PET/CT with standard procedure on a dedicated scanner before the therapy onset. When the PET scan turned out positive for IE, SUV max was measured. Correlation between CRP and SUV max was calculated. ROC curves of PET sensitivity were built. RESULTS: 29/55 had a final diagnosis of IE on the basis of echocardiography, Duke criteria, blood cultures, physical exam and serological markers of inflammation. 19 patients had a positive PET/CT scan while 1 presented an equivocal PET result. In PET positive patients, there was not a significant correlation between the serum level of CRP and SUV max (p= 0,94). With a CRP cut-off =7,86 mg/dl, the sensitivity of PET/CT was 82.4% and specificity was 42.9%. Conclusion: According to our preliminary result, CRP serum level could be used to optimize the employment of FDG PET/CT