Impact of a structured quantitative program on [18F]FP-CIT PET interpretation: a multicenter study of diagnostic accuracy, interrater reliability, and reader confidence

OBJECTIVES: This study assessed the impact of a structured quantitative analysis program on diagnostic performance, interrater reliability, and reader confidence in interpreting N-3-[18F]fluoropropyl-2β-carbomethoxy-3β-4-iodophenyl nortropane positron emission tomography ([18F]FP-CIT PET) scans to differentiate idiopathic Parkinson's disease from essential tremor-/drug-induced parkinsonism. METHODS: This retrospective multicenter study included 637 patients who underwent [18F]FP-CIT PET and brain magnetic resonance imaging scans for evaluation of Parkinsonian syndromes at 4 institutions between January 2015 and October 2022. Readers evaluated the scans qualitatively in the pre-program session and with access to quantitative parameters in the post-program session, with a 1-month minimum interval to minimize recall bias. Diagnostic performance metrics (sensitivity, specificity, accuracy), interrater reliability (Cohen's κ), and reader confidence (low/moderate vs high) were compared. RESULTS: Following program implementation, interrater reliability significantly improved from substantial to almost perfect (Cohen's κ: 0.768-0.970; P < .001), and a significant shift toward high-confidence ratings was observed (P < .001). Diagnostic accuracy also significantly improved from 92.8% to 94.3% (P = .036). Although the increase in the area under the curve (0.922-0.932) did not reach statistical significance (P = .163), likely due to a ceiling effect, reader performance significantly surpassed that of the quantitative parameter alone only after program implementation, whereas it was comparable at baseline. CONCLUSIONS: These findings suggest that integrating quantitative analysis tools may improve diagnostic consistency and reliability in clinical practice. ADVANCES IN KNOWLEDGE: The structured quantitative analysis program significantly improved [18F]FP-CIT PET/CT interpretation by increasing diagnostic accuracy, interrater reliability, and reader confidence.