Comparison of visual criteria for amyloid-PET reading: could their merging reduce the inter-raters variability?

Barbara Paghera, Daniele Altomare, Alessia Peli, Silvia Morbelli, Ambra Buschiazzo, Matteo Bauckneht, Raffaele Giubbini, Carlo Rodella, Luca Camoni, Marina Boccardi, Cristina Festari, Cristina Muscio, Alessandro Padovani, Giovanni B Frisoni, Ugo P Guerra

Research output: Contribution to journalArticlepeer-review


BACKGROUND: Three different amyloid tracers labeled with 18-flourine have been introduced into clinical use. The leaflets of tracers indicate different visual criteria for PET reporting. In clinical practice, it isn't yet ascertained whether this criteria are equivalent in terms of diagnostic accuracy or if anyone is better than another. We aimed to evaluate the inter and intra-rater variability of visual assessment of 18F-Florbetapir PET/CT images among six independent readers with different clinical experience.

METHODS: We analyzed 252 PET/CT scans, visually assessed by each reader three times, applying independently the three different reading criteria proposed. Each reader evaluated the regional uptake specifying for each cortical region a numeric value of grading of positivity in order to assign a final score. At the end of each reading a level of confidence was determined by assigning a score from 0 (negative) to 4 (positive). After first reading, those cases in which the evaluations by two experienced readers did not match (discordant cases) were independently reevaluated merging all the three different visual interpretation criteria.

RESULTS: Good agreement was observed for visual interpretation among the six readers' confidence-level using independently the three visual reading criteria: ICC=0.83(0.80-0.86) for 18F-Florbetapir, ICC=0.84(0.81-0.87) for 18F-Florbetaben, and ICC=0.86(0.83-0.88) for 18F-Flutemetamol reading. A good inter-rater agreement was observed for final-score too: ICC=0.74(0.70-0.78) for 18F-Florbetapir; ICC=0.82(0.79-0.85) for 18F-Florbetaben; ICC=0.84(0.81-0.87) for 18F-Flutemetamol. Intra-rater agreement was good for final-score (from 0.76 to 0.90; p<0.001) and confidence-level (Spearman's rho from 0.89 to 1.00; p<0.001). Disagreement between the two experienced readers was observed in 22/252 cases (9%). The agreement converged over a second round of independent reading in 12/22 cases (54%), by merging all the criteria.

CONCLUSIONS: All the criteria proposed are useful to determine the grading of positivity or negativity of amyloid deposition and their merging improves the diagnostic confidence and provides a better agreement.

Original languageEnglish
Pages (from-to)414-421
Number of pages8
JournalQuarterly Journal of Nuclear Medicine and Molecular Imaging
Issue number4
Publication statusPublished - 2020


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