External quality assurance for image grading in the Scottish Diabetic Retinopathy Screening Programme

Area of Science:

• Ophthalmology
• Medical Imaging
• Public Health

Background:

• Diabetic retinopathy screening programs require accurate image grading to detect disease.
• External quality assurance (EQA) is crucial for maintaining grading standards.
• The Scottish Diabetic Retinopathy Screening Programme sought to enhance its EQA system.

Purpose of the Study:

• To develop and evaluate a web-based EQA system for the Scottish Diabetic Retinopathy Screening Programme.
• To assess the performance of image graders and identify areas for improvement.

Main Methods:

• A web-based image grading system was developed, mirroring the national screening software.
• Two rounds of EQA were conducted using 100 images each, comparing grader results to a consensus standard.
• Feedback and guidance notes were provided between rounds to improve performance.

Main Results:

• Grader sensitivity remained high (median 92.5%) in both rounds.
• Specificity improved from a median of 86% in 2008 to 88% in 2010.
• Overall agreement improved after the first round, with no significant differences between centers in 2010.

Conclusions:

• The developed EQA system is a valuable educational tool for improving image grading.
• The system effectively supports quality assurance in diabetic retinopathy screening.
• Continuous evaluation and feedback enhance grading performance and consistency.