Evaluation of Spleen Glucose Metabolism Using ¹⁸F-FDG PET/CT in Patients with Febrile Autoimmune Disease

Abstract

The purpose of this study was to evaluate the clinical significance of ¹⁸F-FDG uptake by the spleen in patients with autoimmune disease. <b>Methods:</b> We retrospectively reviewed Severance Hospital’s electronic medical records of patients hospitalized for the evaluation of fever who underwent ¹⁸F-FDG PET/CT. We found 91 patients with autoimmune diseases and 101 patients with localized infection. ¹⁸F-FDG uptake was assessed by measuring SUV in the spleen and liver. The spleen-to-liver ratio of the SUV_mean (SLR_mean) was calculated. Clinical and laboratory parameters were collected and evaluated for association with SLR_mean. In-hospital mortality was defined as all-cause mortality during hospital admission for fever. <b>Results:</b> SLR_mean was significantly higher in autoimmune disease than in localized infectious disease (1.28 ± 0.43 vs. 0.91 ± 0.21, <i>P</i> &lt; 0.001). In autoimmune disease, SLR_mean was correlated with monocytes, aspartate aminotransferase, alanine aminotransferase, albumin, and ferritin. Analysis of receiver-operating-characteristic curves revealed that in comparison with laboratory parameters, SLR_mean had the highest performance in differentiating autoimmune from localized infectious disease. Multivariate logistic regression analysis demonstrated that high SLR_mean and low platelets were significantly associated with in-hospital mortality in febrile autoimmune disease. <b>Conclusion:</b> These findings suggest that spleen glucose metabolism is increased in febrile autoimmune disease. Spleen ¹⁸F-FDG uptake may provide information useful in differentiating febrile autoimmune disease from localized infectious disease and predicting clinical outcomes in febrile autoimmune disease.