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T. Peto, W. P. Patton, A. K. Muldrew, P. Lenfestey, B. Reeves, S. P. Harding, U. Chakravarthy, VPDT Cohort Study Team; Concordance of Fluorescein Angiography Grading at the Network of Ophthalmic Reading Centres in the United Kingdom. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2248.
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The Network of Ophthalmic Reading Centres of United Kingdom (NetwORC UK) carries out grading of colour fundus and fluorescein angiography (FFA) images of patients enrolled in the Verteporfin Photodynamic Therapy (VPDT) Cohort Study in the United Kingdom. The aim of this study is to present the results of the ongoing grading concordance exercises.
FFA images of 10 study eyes undergoing PDT treatment were selected from the NetwORC imaging database out of 6833 quality controlled angiograms graded during the previous 24 months. Selection criteria were that the images exhibited the full range of typical disease characteristics. All images were independently graded by both Reading Centre experts at each centre and by nine accredited graders from the 3 sites. Area of classic and occult choroidal neovascularisation (CNV), blood, elevated blocked fluorescence (EBF), total lesion and serous pigment epithelial detachment (SPED) were measured together with non-lesion components such as fibrosis, geographic and non-geographic atrophy and laser scar. All lesions were categorised into one of seven lesion subtypes.
In 8 out of 10 angiograms, the 3 experts were in either complete agreement or had one-step difference in lesion subtype categorisation. The same level of agreement was found in 6 out of 10 angiograms by graders. Overall, the intraclass correlation for the ten FFAs and 12 graders was 0.71. Discordance mainly arose when assessing the contribution of occult CNV and the presence and extent of fibrosis. Interestingly, EBF was slightly more discordant amongst graders than experts.
There was good concordance amongst experts, and on lesion subtype among experts and graders combined. The intraclass correlation is in keeping with the level of concordance previously reported for quality assurance exercises. Fibrosis and EBF were the most difficult areas for the graders. Where systematic discrepancies were found, individual, supervised training were given. Based on this study, NetwORC UK continues to operate effectively by using common training and quality control guidelines regardless physical separation of sites.
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