From the Guidelines
PET-CT is a highly valuable diagnostic tool for evaluating Fever of Unknown Origin (FUO), as it can aid in identifying the etiology and guide further investigations or treatment, with a potential cost-effectiveness when performed early in the diagnostic work-up 1.
Key Points to Consider
- The results of [18 F]FDG PET/CT can help identify the cause of FUO, allowing for targeted treatment and potentially improving patient outcomes 1.
- A negative [18 F]FDG PET/CT can predict a favorable prognosis, suggesting spontaneous remission of fever and potentially allowing a watchful waiting approach 1.
- The cost-effectiveness of [18 F]FDG PET/CT has been demonstrated, particularly when performed early in the diagnostic work-up of FUO 1.
Diagnostic Approach
- PET-CT should be considered early in the diagnostic workup of FUO, after initial tests such as blood cultures and basic imaging have failed to identify a cause.
- The procedure involves injecting a radioactive glucose analog (18F-FDG) followed by whole-body scanning, which takes about 2-3 hours total.
- PET-CT is particularly useful for detecting occult infections, hidden malignancies, and non-infectious inflammatory disorders that might be missed by conventional imaging.
Limitations and Considerations
- The main limitations of PET-CT include false positives from physiologic uptake, recent surgery sites, or benign conditions, and false negatives in conditions with low metabolic activity or small lesions.
- PET-CT is most effective when used as part of a comprehensive diagnostic approach rather than in isolation.
- The recent guideline from the European Journal of Nuclear Medicine and Molecular Imaging 1 provides the most up-to-date and highest quality evidence for the use of PET-CT in evaluating FUO.
From the Research
Utility of PET CT for Evaluation of FUO
- The utility of PET CT in evaluating Fever of Unknown Origin (FUO) has been studied extensively, with various studies indicating its effectiveness in diagnosing the underlying cause of FUO 2, 3, 4, 5, 6.
- PET CT has been shown to have superior sensitivity compared to diagnostic CT, with a sensitivity of 88.7% and specificity of 80.9% in one study 2.
- The diagnostic contribution of 18F-FDG PET/CT in identifying the underlying cause of FUO has been evaluated, with results showing that it can precisely detect the cause of fever in 60% of cases 3.
- FDG-PET/CT has been found to have a higher accuracy compared to anatomic imaging in suggesting a cause of FUO, with a sensitivity of 90%, specificity of 97%, and accuracy of 92.2% 4.
- The use of 18F-FDG PET and PET/CT in FUO has been reviewed, with results indicating that it has the potential to play a central role as a second-line procedure in the management of patients with FUO 5.
- Clinical and laboratory variables have been found to have an impact on the diagnostic performance of 18F-FDG PET/CT in patients with FUO, with patients who are most likely to benefit from the PET/CT study being those with several positive inflammation markers 6.
Key Findings
- PET CT is a useful diagnostic tool in evaluating FUO, with high sensitivity and specificity 2, 3, 4.
- The use of 18F-FDG PET/CT can help establish the fever origin in a significant number of cases, especially in patients with infection or neoplasm, and vasculitis, autoimmune disease or non-infectious inflammatory disease 3, 6.
- The diagnostic performance of 18F-FDG PET/CT can be influenced by clinical and laboratory variables, such as inflammation markers and culture results 6.