Utility of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in COVID-19 infection- a single centre retrospective observational study

ABSTRACT

Aim/Introduction: Although 18F-Fluorodeoxyglucose (FDG) Positron Emission Tomography/Computed Tomography (PET/ CT) is not routinely used for diagnosis of COVID- 19 infections, we incidentally detected lung lesions in few patients, who were referred for some other indications. The study aimed to explore a cut off value of standardized uptake values (SUV) of 18F-FDG PET/ CT in predicting active COVID-19 infection in both symptomatic and asymptomatic patients referred to our department for various oncologic indications. Material(s) and Method(s) We retrospectively analysed PET/CT studies performed from March 2020 to August 2021 done at our department, who underwent 18F-FDG PET/CT for various oncological indications. PET/CT scans were reviewed by 2 experienced nuclear medicine physicians. At first, only HRCT chest was reviewed to ascertain inclusion of the patient. CT severity score and COVID-19 Reporting and Data System (CORADS) criteria were calculated from HRCT chest. PET/CT images were reviewed and SUVmax were recorded in lung parenchyma and mediastinal blood pool and SUV ratios (SUVR) between them were calculated. Result(s) A total of 85 patients were identified and divided into 3 groups based on clinical symptoms and reverse transcription-polymerase chain reaction (RT-PCR) results * Group A- patients with symptoms of COVID- 19 and positive RT-PCR- (n=51) * Group B- patients with symptoms of COVID-19 and a negative RT-PCR- (n=13) * Group Cpatients with no symptoms of COVID-19 - (n=21). SUVR of these 3 groups (2.67+/-1.21 vs 1.86+/-0.8 vs 1.42+/-0.53 respectively) showed significant statistical difference (p<0.05). Moderate correlation was obtained between SUVR and CT severity score (r= 0.43, p<0.05), thereby correlating towards prognosis. The area under the curve (AUC) obtained for different cut-off values of SUVR was 0.74 (95% CI- 0.55-0.97, p<0.05). A SUVR cut-off value of 1.87 yielded a specificity of at least 74.3% and a sensitivity of at least 68%. Conclusion(s) An SUVR cut off value of 1.87 can yield a specificity of at least 74.3% and a sensitivity of at least 68%. HRCT chest and 18F-FDG PET/CT plays a complementary role in determining active COVID-19 infection. SUVR of pulmonary lesions can be considered as an important prognostic indicator for active COVID-19 infections.