Utility of FDG-PET/CT in clinical psoriasis grading: the PET-PASI scoring system

Psoriatic skin lesions are metabolically active, which makes them candidates for imaging with 18-F fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT). The aim of our study was to correlate FDG-PET findings with Psoriasis Area and Severity Index (PASI) scores, the most widely-used grading system for psoriasis. Thirty-three subjects and a total of 84 FDG-PET/CT scans from a prospective clinical trial [NCT01553058] with >2 months moderate-to-severe psoriasis were included. Subjects underwent whole-body FDG-PET/CT imaging 60 min after intravenous FDG administration, prior to the start of treatment. Scans were repeated 12 weeks and 52 weeks after baseline scans were conducted and after treatment or placebo administration was initiated. Each subject and scan was graded by our "PET-PASI" scoring system, a qualitative review of multi-plane reconstructions for both attenuation-corrected (AC) and non-attenuation-corrected (NAC) PET images. PASI and PET-PASI scores were correlated using Spearman's rho analysis. Our study demonstrated a significant positive correlation between each subject's corresponding PET-PASI and PASI scores before and during treatment or placebo administration (r=0.53, P<0.001). We also found positive correlations between PET-PASI and PASI scores across different regions of the body (head and neck: r=0.22, upper extremities: r=0.26, trunk: r=0.48, and lower extremities: r=0.58). In conclusion, AC and NAC FDG-PET/CT images may be utilized to evaluate lesions in subjects with moderate-to-severe psoriasis. Our methodology could have future implications in the diagnosis and therapeutic management of psoriasis.