Systemic quality control of performance, also called inter-institute quality control, is required for all partner institutions, including general medical institutions and third-party service centers. All kinds of DR reading procedures, including screening reading, general diagnostic reading, and quantitative diagnostic reading, should be included in the systemic performance evaluation.
The process of systemic quality control includes sampling of all kinds of DR readings from each institute followed the systemic repetitive readings and comparative analysis with the same procedure by a reference reading center or by Diabetic Retinopathy Image Diagnosis Quality Assurance Service Center (QASC). 
Systemic quality control is a process of retrospective analysis on the performance of the general medical institutions and third-party reading centers. The purpose of systemic quality control is to keep the consistency of quality performance of DR reading from every individual physician, medical institutions, and independent DR reading centers. The results of systemic quality control will not affect the existing DR reading reports, but will be used for continuing improvement of performance of the readers or reading centers.