Evaluation of spleen glucose metabolism using ¹⁸F-FDG PET/CT in patients with febrile autoimmune disease

The purpose of this study was to evaluate the clinical significance of ¹⁸F-FDG uptake by the spleen in patients with autoimmune disease. Methods: 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 SUVmean (SLRmean) was calculated. Clinical and laboratory parameters were collected and evaluated for association with SLRmean. In-hospital mortality was defined as all-cause mortality during hospital admission for fever. Results: SLRmean was significantly higher in autoimmune disease than in localized infectious disease (1.28 6 0.43 vs. 0.91 6 0.21, P , 0.001). In autoimmune disease, SLRmean was correlated with monocytes, aspartate aminotransferase, alanine aminotransferase, albumin, and ferritin. Analysis of receiver-operating-characteristic curves revealed that in comparison with laboratory parameters, SLRmean had the highest performance in differentiating autoimmune from localized infectious disease. Multivariate logistic regression analysis demonstrated that high SLRmean and low platelets were significantly associated with in-hospital mortality in febrile autoimmune disease. Conclusion: 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.