The extra-cardiac work-up in infective endocarditis (IE) comprises a search for primary and secondary infective foci. Whether 18FDG-PET/CT or WBC-SPECT/CT is superior in detection of clinically relevant extra-cardiac manifestations in IE is unexplored. The objectives of this study were to identify the numbers of positive findings detected by each imaging modality, to evaluate the clinical relevance of these findings and to define the reproducibility for extra-cardiac foci in patients with definite IE. Each modality was evaluated for numbers and location of positive extra-cardiac foci in patients with definite IE. A team of 2 × 2 cardiologists evaluated each finding to determine clinical relevance. Clinical utility was determined by 4 criteria converted into an ordinal scale. Using the manifestation with highest clinical utility rating in each patient, the clinical impact of the two imaging modalities was expressed in a clinical utility score. To evaluate reproducibility for each modality, an imaging core laboratory reviewed all findings. In 55 IE patients, 91 pathological foci were found by FDG-PET/CT and 37 foci were identified by WBC-SPECT/CT (p < 0.001). The clinical utility of FDG-PET/CT was significantly higher than that of WBC-SPECT/CT when comparing clinical utility score (2.06 vs. 1.17; p = 0.01). In assessment of extra-cardiac diagnostics in IE, inter-observer reproducibility was substantial for WBC-SPECT/CT (k 0.69, 95% CI 0.49-0.89) and substantial to excellent for FDG-PET/CT (k 0.79, 95% CI 0.61-0.98). FDG-PET/CT has a significantly higher clinical utility score than WBC SPECT/CT and is potentially superior to WBC-SPECT/CT in detection of extra-cardiac pathology in patients with IE.
Keywords: Infectious foci; Infective endocarditis; PET/CT; Reproducibility; SPECT/CT.