J Korean Med Sci.  2021 Jun;36(22):e150. 10.3346/jkms.2021.36.e150.

Predictors of Diagnostic Contributions and Spontaneous Remission of Symptoms Associated with Positron Emission Tomography with Fluorine-18-Fluorodeoxy Glucose Combined with Computed Tomography in Classic Fever or Inflammation of Unknown Origin: a Retrospective Study

• Tsuzuki S
• Tsuzuki S
• Watanabe A
• Watanabe A
• Iwata M
• Iwata M
• Toyama H
• Toyama H
• Terasawa T
• Terasawa T

• KMID: 2516580
• DOI: http://doi.org/10.3346/jkms.2021.36.e150

Abstract

Background
In patients with fever or inflammation of unknown origin (fever of unknown origin [FUO] or inflammation of unknown origin [IUO], respectively), expert consensus recommends the use of positron emission tomography with fluorine-18-fluorodeoxy glucose combined with computed tomography (FDG-PET/CT) when standard work-up fails to identify diagnostic clues. However, the clinical variables associated with successful localization of the cause by FDG-PET/CT remain uncertain. Moreover, the long-term outcomes of patients with unexplained FUO or IUO after negative FDG-PET/CT results are unknown. Therefore, we assessed predictors of successful diagnosis of FUO or IUO caused by FDG-PET/CT and associations of spontaneous remission of symptoms with FDG-PET/CT results.
Methods
All patients with FUO or IUO, who underwent FDG-PET/CT from 2013 to 2019 because diagnostic work-up failed to identify a cause, were retrospectively included. We calculated the diagnostic yield and performed multivariable logistic regression to assess characteristics previously proposed to be associated with successful localization of FUO or IUO causes. We also assessed whether the FDG-PET/CT results were associated with spontaneous remissions.
Results
In total, 50 patients with diagnostically challenging FUO or IUO (35 with FUO and 15 with IUO) were assessed. Other than one case of infection, all the identified causes were either malignancy or non-infectious inflammatory diseases (each with 18 patients), and FDG-PET/ CT correctly localized the cause in 29 patients (diagnostic yield = 58%). None of the proposed variables was associated with successful localization. All 13 patients with sustained unexplained cause remained alive (median follow-up, 190 days). Spontaneous remission was observed in 4 of 5 patients with a negative FDG-PET/CT, and 1 of 8 with a positive result (P = 0.018).
Conclusion
In the current cohort, the proposed variables were not predictive for successful localization by FDG-PET/CT. A negative FDG-PET/CT scan may be prognostic for spontaneous remission in patients with sustained FUO or IUO.

Keyword

Diagnosis; Fever of Unknown Origin; Inflammation; Positron Emission Tomography Computed Tomography; Spontaneous Remission

Figure

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  Fig. 1 Study design.FDG = fluorodeoxyglucose, PET = positron emission tomography, CT = computed tomography, TP = true positive, FP = false positive, FN = false negative, TN = true negative, FUO = fever of unknown origin, IUO = inflammation of unknown origin.

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  Fig. 2 Prognosis of patients with FUO or IUO assessed by FDG-PET/CT. Kaplan-Meier plots showing the overall survival of all 50 patients by FUO or IUO etiology (A), positivity of FDG-PET/CT (B), and cumulative probability of spontaneous remission of symptoms by positivity of FDG-PET/CT (C).OS = overall survival, FUO = fever of unknown origin, IUO = inflammation of unknown origin, FDG = fluorodeoxyglucose, PET = positron emission tomograph, CT = computed tomography.

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