key: cord-0901348-ifz71s8n
authors: Treglia, Giorgio
title: The role of (18)F-FDG PET for COVID-19 infection: myth versus reality
date: 2020-04-30
journal: Clin Transl Imaging
DOI: 10.1007/s40336-020-00367-z
sha: 0e632467c4b52f21c08cb8178ba7b2edde9053fd
doc_id: 901348
cord_uid: ifz71s8n

nan

that cells involved in infection and inflammation, especially neutrophils and the monocyte/macrophage family, are able to express high levels of glucose transporters and hexokinase activity. Notably, 18 F-FDG PET/CT may early detect pathophysiological changes in affected tissues in patients with infectious or inflammatory diseases and these functional changes may occur before anatomical changes detected by conventional imaging techniques. Enough evidence-based data in the literature already exist about the usefulness of 18 F-FDG PET/CT in the diagnosis and management of several infectious and inflammatory diseases [2] .

Recently, some case reports and small case series have shown 18 F-FDG PET/CT findings in patients with acute respiratory disease caused by COVID-19 infection. In particular, in the most large series described by Qin et al. [3] , 18 F-FDG PET/CT results from four patients with suspicious COVID-19 infection were described. The patients were admitted to the hospital with respiratory symptoms and fever when the COVID-19 outbreak was still unrecognized and the virus infectivity was unknown. All patients had typical chest CT imaging features of the COVID-19 pneumonia as described above. At 18 F-FDG PET/CT, lung lesions were characterized by increased 18 F-FDG uptake and there was evidence of lymph node involvement. Conversely, disseminated disease was absent suggesting that COVID-19 has pulmonary tropism. In their conclusion, the authors suggested a potential clinical usefulness of 18 F-FDG PET/CT in patients with suspicious COVID-19 infection, especially at early stages when clinical symptoms are not specific and differential diagnosis is challenging [3] .

Unfortunately, based on objective data, the "myth" of the potential usefulness of 18 F-FDG PET/CT in patients with known or suspicious COVID-19 infection (as suggested by Qin et al.) collides with the "reality".

The findings of increased metabolic activity in pulmonary or lymph nodal lesions in patients with COVID-19 infection is not surprising as acute inflammatory and infectious pulmonary lesions are usually characterized by increased 18 F-FDG uptake. Furthermore, these 18 F-FDG PET/CT findings are not specific for COVID-19 infection, and they cannot be used for the differential diagnosis of pulmonary infections or inflammatory diseases. 18 F-FDG PET/CT should not be recommended for the evaluation of patients with known or suspicious COVID-19 infection. Chest CT remains the suggested imaging method to evaluate COVID-19 pneumonia and it is yet demonstrated that radiological pattern is more accurate than RT-PCR. There are currently no data suggesting an added value of 18 F-FDG PET/CT compared to chest CT in the management or outcome of patients with COVID-19 infection. Conversely, 18 F-FDG PET/CT is more complex than chest CT leading a possible increased risk of disease spreading due to the longer time of 18 F-FDG PET/CT procedure compared to chest CT. Most importantly, specific safety and prevention protocols should be followed in the Nuclear Medicine departments during the outbreak of COVID-19 to allow for safe nuclear medicine diagnosis and treatment procedures [4, 5] .

Therefore, the hypothesis that 18 F-FDG PET/CT is useful in the evaluation of COVID-19 pneumonia due to the peculiar metabolic behavior of this infection is excessive and not clearly demonstrated until now. On the other hand, nuclear medicine physicians should pay attention to incidental CT findings of interstitial pneumonia (with ground-glass opacities) suspected for COVID-19 infection detected at 18 F-FDG PET/CT, as demonstrated by some recent reports [6, 7] . In clinical practice, the risk to have asymptomatic patients with COVID-19 infection who undergo nuclear medicine procedures including 18 F-FDG PET/CT is not negligible [6, 7] and this is the "reality" about 18 F-FDG PET/CT and COVID-19 infection.

Conflict of interest The author declares that he has no financial or nonfinancial competing interests.

Ethical approval This article does not contain any studies with human participants or animals.

Imaging and clinical features of patients with 2019 novel coronavirus SARS-CoV-2

Diagnostic performance of 18 F-FDG PET/CT in infectious and inflammatory diseases according to published meta-analyses

18 F-FDG PET/CT findings of COVID-19: a series of four highly suspected cases

Suggestions for safety and protection control in Department of Nuclear Medicine during the outbreak of COVID-19

COVID-19 pandemic: guidance for nuclear medicine departments

Incidental CT findings suspicious for Covid-19 associated pneumonia on nuclear medicine exams: recognition and management plan

Incidental findings suggestive of COVID-19 in asymptomatic patients undergoing nuclear medicine procedures in a high prevalence region