¹⁸F-FDG-PET/CT in unexplained elevated inflammatory markers. Joining entities

The diagnostic strategy in patients with fever or inflammation of unknown origin remains a major clinical challenge. The aim of this study was to evaluate the role of ¹⁸F-FDG-PET/CT in patients with unexplained elevated C-reactive protein with or without fever. Contribution of ¹⁸F-FDG-PET/CT to the final diagnosis was evaluated. In addition we determined whether a differentiation between patients with or without fever is clinically reasonable.

We retrospectively analysed 72 consecutive patients with unexplained elevated C-reactive protein levels (above 8mg/l) that underwent ¹⁸F-FDG-PET/CT in our facility between 10/2009 and 11/2012. ¹⁸F-FDG-PET/CT was considered a so-called diagnostic scan when results decisively led to a final diagnosis and adequate therapy with a response of symptoms was initiated due to the PET/CT result.

In 60/72 patients (83%) a final diagnosis was established. Diagnoses included infections (58%), non-infectious inflammatory diseases (29%) and malignancies (8%). ¹⁸F-FDG-PET/CT was true positive in 47 cases (65%) and the diagnostic scan in 29 patients (40%). Sensitivity of ¹⁸F-FDG-PET/CT was 81% and specificity was 86%. Diagnostics, final diagnoses, ¹⁸F-FDG-PET/CT results, SUVmax, C-reactive protein levels and the diagnostic scan did not differ significantly between patients with fever and patients without fever.

¹⁸F-FDG-PET/CT is a useful method in the diagnostic workup of patients with inflammation of unknown origin. In our series there was no significant difference between patients with or without fever. Regarding ¹⁸F-FDG-PET/CT-imaging inflammation of unknown origin and unexplained fever can be joined to one entity.