ORIGINAL ARTICLE   

The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2020 December;64(4):414-21

DOI: 10.23736/S1824-4785.19.03124-8

Copyright © 2019 EDIZIONI MINERVA MEDICA

language: English

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

Barbara PAGHERA ¹ ✉, Daniele ALTOMARE ^{2, 3}, Alessia PELI ¹, Silvia MORBELLI ⁴, Ambra BUSCHIAZZO ⁴, Matteo BAUCKNEHT ⁴, Raffaele GIUBBINI ¹, Carlo RODELLA ¹, Luca CAMONI ¹, Marina BOCCARDI ^{2, 5}, Cristina FESTARI ^{2, 6}, Cristina MUSCIO ^{2, 7}, Alessandro PADOVANI ⁸, Giovanni B. FRISONI ^{2, 4, 9}, Ugo P. GUERRA ¹⁰

¹ Department of Nuclear Medicine, University of Brescia, Brescia, Italy; ² Laboratory of Alzheimer’s Neuroimaging and Epidemiology (LANE), San Giovanni di Dio Clinical Research Center, Brescia, Italy; ³ Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy; ⁴ Department of Nuclear Medicine, San Martino University Hospital and IRCCS, Genoa, Italy; ⁵ Laboratory of Neuroimaging of Aging (LANVIE), University of Geneva, Geneva, Switzerland; ⁶ Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy; ⁷ Division of Neurology V - Neuropathology, Carlo Besta Institute of Neurology Foundation and IRCCS, Milan, Italy; ⁸ Unit of Neurology, Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy; ⁹ Memory Clinic, University Hospital of Geneva, Geneva, Switzerland; ¹⁰ Department of Nuclear Medicine, Poliambulanza Foundation, Brescia, Italy

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 is not yet ascertained whether these 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 of 252 cases (9%). The agreement converged over a second round of independent reading in 12 of 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.

KEY WORDS: Positron emission tomography computed tomography; Amyloid; Observer variation