Analysis of the diagnostic effect of 18F-FDG PET/CT in IIM patients and its relationship with disease severity.

Objective: To analyze the diagnostic effect of fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) in patients with idiopathic inflammatory myopathies (IIM) and its relationship with disease severity.

Subjects and methods: A retrospective analysis was conducted on the clinical and imaging data of 31 IIM patients treated in our hospital from April 2020 to April 2024, who were included in the lesion group. Additionally, 30 patients without muscle disease during the same period were selected as the control group. The maximum standardized uptake value (SUVmax) of the proximal limb girdle muscles was measured in both groups and compared. A receiver operating characteristic (ROC) curve was plotted to analyze the diagnostic value of SUVmax for IIM using ¹⁸F-FDG PET/CT. Spearman rank correlation was used to analyze the relationship between muscle SUVmax in IIM patients and relevant laboratory indicators, including creatine kinase (CK), creatine kinase-MB (CK-MB), C-reactive protein (CRP), serum ferritin (SF), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT).

Results: The SUVmax level of the lesion group (2.94±0.58) was significantly higher than that of the control group (1.17±0.23) (t=15.568, P<0.05). A receiver operating characteristic curve analysis indicated that the optimal cut-off value of SUVmax for distinguishing the lesion group from the control group was 2.16g/mL, with a diagnostic sensitivity of 100%, specificity of 91.8%, and an area under the curve (AUC) of 0.952. Correlation analysis showed a positive correlation between SUVmax and CK (r=0.659), CK-MB (r=0.523), AST (r=0.458), and LDH (r=0.437) (P<0.05), but no significant correlation with CRP (r=0.219), SF (r=0.348), or ALT (r=0.237).

Conclusion: Fluorine-18-FDG PET/CT demonstrates an ideal diagnostic effect for IIM patients, and its semi-quantitative parameter, SUVmax, holds good auxiliary diagnostic value for IIM. It can reflect the activity and severity of the disease to a certain extent.