Population	Male and female adults ≥ 18 years of age of any ethnicity with less than HRC‐PDR, diagnosed as per standard clinical protocol
Index prognostic factors	We anticipated that less information would be available regarding prognostic factors associated with progression from PDR to HRC‐PDR.   Prognostic factors of interest included: routinely collected patient demographics and information, such as age, gender, ethnicity, socioeconomic status, and smoking habits; frequently obtained standard clinical data, such as comorbidities (presence/absence of cardiovascular disease; cerebrovascular disease; nephropathy, and specifically, chronic kidney failure (defined as estimated GFR of < 60 mL/min/1.73 m2); peripheral neuropathy); BMI, neck/waist circumference; glycated haemoglobin; blood pressure; low‐density lipoprotein; high‐density lipoprotein; and triglycerides; and functional and structural retinal biomarkers in the prognostic context of the development and progression of HRC‐PDR.   The scope of this review did not extend to the evaluation of the effect of treatment on progression to HRC‐PDR. Given this, we considered prognostic factors in the absence of previous treatment for PDR.   Prognostic factors were generally measured at the time participants entered the studies, and indeed, after the diagnosis of less than HRC‐PDR. However, where measures of prognostic factors were available at other time points, and these coincided in more than one included study, we investigated them at these other time points. We did not consider prognostic factors that ‐ to be measured ‐ require invasive procedures (e.g. aqueous or vitreous samples to measure growth factors in these fluids) not performed in routine clinical practice.
Comparator	Not applicable
Outcomes	Progression from PDR to HRC‐PDR.
Timing	3 years (± 2 years), 8 years (± 2 years), or lifelong, if available. HRC‐PDR can occur very rapidly ‐ in days ‐ or take months or years to develop.
Setting	Any clinical setting. No geographical limitations