Investigating the potential added value of [(18)F]FDG-PET/CT in long COVID patients with persistent symptoms: a proof of concept study

Since the end of 2019, the coronavirus disease 2019 (COVID-19) virus has infected millions of people, of whom a significant group suffers from sequelae from COVID-19, termed long COVID. As more and more patients emerge with long COVID who have symptoms of fatigue, myalgia and joint pain, we must examine potential biomarkers to find quantifiable parameters to define the underlying mechanisms and enable response monitoring. The aim of this study is to investigate the potential added value of [(18)F]FDG-PET/computed tomography (CT) for this group of long COVID patients. METHODS: For this proof of concept study, we evaluated [(18)F]FDG-PET/CT scans of long COVID patients and controls. Two analyses were performed: semi-quantitative analysis using target-to-background ratios (TBRs) in 24 targets and total vascular score (TVS) assessed by two independent nuclear medicine physicians. Mann–Whitney U-test was performed to find significant differences between the two groups. RESULTS: Thirteen patients were included in the long COVID group and 25 patients were included in the control group. No significant differences (P < 0.05) were found between the long COVID group and the control group in the TBR or TVS assessment. CONCLUSION: As we found no quantitative difference in the TBR or TVS between long COVID patients and controls, we are unable to prove that [(18)F]FDG is of added value for long COVID patients with symptoms of myalgia or joint pain. Prospective cohort studies are necessary to understand the underlying mechanisms of long COVID.