Reproducibility of SIMPLE classification for diabetic retinopathy screening and its comparison to current Italian guidelines

Abstract

Purpose To evaluate the reproducibility of SIMPLE (Single field Image Multi Parameters defined Lesions Extent), a new Diabetic Retinopathy (DR) classification for screening of 45° single field fundus pictures of patients with diabetes (PwDM), assessing DR, Diabetic Maculopathy (DMac) and referral rate agreement and comparing it to current Italian Guidelines (IG). Materials and methods We conducted a retrospective, observational, multicentre study, collecting 1000 retinal 45° single field images of PwDM obtained during routine visits in two diabetes clinics. Three ophthalmologists evaluated each image, determining the presence and number of specific DR lesions and then assigning a stage according to the current IG for screening. SIMPLE staging was performed automatically via Excel software, based on the pre-specified DR characteristics observed by the graders. We analysed intra-centre, inter-centre and total inter-grader agreement for DR and DMac stage and referral rate of the two classifications. Results Agreement amongst the three graders was consistently higher when using SIMPLE classification than when using current IG classification. For DR, kappa (k) was 0.86 with IG and 0.95 with SIMPLE classification; for DMac, k-IG was 0.78, while k-SIMPLE was 0.96; concordance on the referral rate was 0.91 with IG and 0.99 with SIMPLE. Similar results were obtained in sub-analyses for the evaluation of intra-centre and inter-centre concordance. Conclusions Our results suggest that the new SIMPLE classification has an excellent reproducibility amongst graders, comparable or superior to the current IG for DR screening proposed in 2015, improving the standardisation of the decision on referability.