Place of the 18F-FDG-PET/CT in the Diagnostic Workup in Patients with Classical Fever of Unknown Origin (FUO).

Simon Letertre,Marie-Christine Picot,Philippe Guilpain,Vincent Le Moing,Jean Ribstein,Denis Mariano-Goulart,Laetitia Zerkowski,Camille Roubille,Pierre Fesler

doi:10.3390/jcm10173831

Abstract

Objective: To explore the diagnostic contribution of the 18F-FDG-PET/CT in a population of patients with classical fever of unknown origin (FUO), to pinpoint its place in the diagnostic decision tree in a real-life setting, and to identify the factors associated with a diagnostic 18F-FDG-PET/CT. Method: All adult patients (aged ≥ 18 years) with a diagnosis of classical FUO who underwent an 18F-FDG-PET/CT in the University Hospital of Montpellier (France) between April 2012 and December 2017 were included. True positive 18F-FDG-PET/CT, which evidenced a specific disease causing FUO, were considered to be contributive. Results: Forty-four patients with FUO have been included (20 males, 24 females; mean age 57.5 ± 17.1 years). Diagnoses were obtained in 31 patients (70.5%), of whom 17 (38.6%) had non-infectious inflammatory diseases, 9 had infections (20.5%), and 3 had malignancies (6.8%). 18F-FDG-PET/CT was helpful for making a final diagnosis (true positive) in 43.6% of all patients. Sensitivity and specificity levels were 85% and 37%, respectively. A total of 135 investigations were performed before 18F-FDG-PET/CT, mostly CT scans (93.2%) and echocardiography (59.1%), and 108 after 18F-FDG-PET/CT, mostly biopsies (including the biopsy of a temporal artery) (25%) and MRIs (34%). In multivariate analysis, the hemoglobin level was significantly associated with a helpful 18F-FDG-PET/CT (p = 0.019, OR 0.41; 95% CI (0.20–0.87)), while the CRP level was not associated with a contributive 18F-FDG-PET/CT. Conclusion: 18F-FDG-PET/CT may be proposed as a routine initial non-invasive procedure in the diagnostic workup of FUO, especially in anemic patients who could be more likely to benefit from 18F-FDG-PET/CT.

Highlights

Based on the screening of 2021 18 F-FDG-positron-emission tomography/computed tomography (PET/CT) tests from the database of the nuclear medicine department between April 2012 and December 2017, according to the inclusion criteria we selected 72 patients who underwent 18 F-FDG-PET/CT to explore an fever of unknown origin (FUO)
In our present study, based on rigorous inclusion criteria and the definition of FUO, we found that 18 F-FDG-PET/CT contributed to the final diagnosis in 43.6% of all patients and 54.8% of patients already having a diagnosis, with a sensitivity of 85% and a specificity of 37%
The present data argue for an 18 F-FDG-PET/CT-based diagnosis of FUO

Summary

Introduction

Fever of unknown origin (FUO) [1,2] is one of the most challenging diagnostic situations, with about 200 possible underlying diagnoses. Classical FUO refers to a prolonged febrile illness for at least 3 weeks, with a body temperature >38.3 ◦ C on several occasions, and without an established etiology despite extended investigations in non-immunocompromised patients [3]. Causes of classical FUO can be stratified into 4.0/). Four categories: noninfectious inflammatory diseases (NIID), infections, malignancies, and miscellaneous causes [4,5]. The diagnostic workup of FUO includes a search for potential diagnostic clues (PDCs) that could help to ascertain a specific diagnosis, based on a complete medical history and symptom-taking, a physical examination, and several investigations, including cultures and standard imaging [6].

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