A new model for diabetic retinopathy screening may decrease the frequency of eye examinations in patients with type 1 diabetes mellitus (T1DM), without delaying the diagnosis of clinically significant eye disease. Findings were recently published online in the New England Journal of Medicine.
The personalized screening schedule was developed from the Diabetes Control and Complications Trial (DCCT) and the Epidemiology of Diabetes Intervention and Complications (EDIC) study and may substantially decrease costs by an estimated $1 billion over 20 years.
The model is based on individual glycemic control and five different states determined by the degree of retinopathy at baseline:
• State 1: No retinopathy
• State 2: Mild nonproliferative retinopathy
• State 3: Moderate nonproliferative retinopathy
• State 4: Severe nonproliferative diabetic retinopathy
• State 5: Proliferative diabetic retinopathy or clinically significant macular edema
“Our data suggest that a practical, evidence-based schedule for time to the next examination would be 4 years, 3 years, 6 months, and 3 months for patients with states 1 through 4, respectively, for which the corresponding cumulative incidence of progression to state 5 retinopathy would be 2.9%, 3.7%, 6.6%, and 14.4%,” wrote author David Nathan, MD, of Harvard Medical School in Boston, and colleagues with the DCCT/EDIC Research Group.
Diabetic retinopathy represents the most common cause of blindness in American adults. Current guidelines recommend annual screening retinal examinations 3 to 5 years after the diagnosis of T1DM. Screening can contribute to earlier detection and intervention, which can greatly decrease vision loss.
To develop the screening schedule, researchers evaluated retinal photographs from the DCCT and EDIC studies. The DCCT trial was conducted from 1983 through 1993 and included 1441 patients with T1DM, of whom 711 were randomized to intensive glucose-lowering therapy and 730 to conventional therapy. The EDIC study includes 1375 participants from the DCCT trial who have been followed up since 1994. Fundus photography was performed every 6 months during the DCCT trial and every fourth year during the EDIC study.
Researchers developed the screening model based on about 24,000 eye evaluations conducted over a follow-up of nearly 30 years. Modeling techniques focused on estimating the likelihood of progression based on baseline retinopathy and hemoglobin A1c (HbA1c), with an acceptable limit of 5% for progression to proliferative retinopathy/macular edema (state 5).
• Screening schedule with 5% probability of progression to proliferative retinopathy/macular edema:
♦ No retinopathy: 4 years
♦ Mild retinopathy: 3 years
♦ Moderate retinopathy: 6 months
♦ Severe nonproliferative retinopathy: 3 months
• 20-Year results using this screening schedule:
♦ Eye examination frequency decreased by 58%
♦ 43.4% decrease in costs compared with annual screening
♦ Estimated $1 billion in cost savings
• HbA1c impact on risk of progression from no retinopathy to proliferative diabetic retinopathy/macular edema:
♦ HbA1c, 6%: 1.0% risk over 5 years
♦ HbA1c, 10%: 4.3% risk over 3 years
♦ Each 1% increase in mean HbA1c was linked to a 15.4% increased risk of progression from no retinopathy to mild retinopathy
Results suggest patients with an HbA1c of 6% and no retinopathy would need an examination at 5 years, while patients with an HbA1c of 10% and no retinopathy would need an examination at 3 years, according to the authors.
They noted that the model was developed from a research cohort and may not apply to other populations. Validation of the model in an independent group of patients is necessary.
• The retinopathy screening model developed from the DCCT and EDIC trials may decrease the frequency of eye examinations and substantially decrease costs.
• The model relies on baseline HbA1c and degree of retinopathy.
• Suggested screening schedules are based on the model: every 4 years for patients with no retinopathy, every 3 years with mild nonproliferative retinopathy, every 6 months with moderate nonproliferative retinopathy, and every 3 months with severe nonproliferative retinopathy.
• The model was developed from a research population and requires validation.
The study was supported by the National Institute of Diabetes and Digestive and Kidney Diseases, the National Eye Institute, and the National Institute of Neurological Disorders and Stroke. Free or discounted research supplies were provided by Abbott Diabetes Care, Animas, Becton Dickinson, Diabetes Care by Bayer, Eli Lilly, Extend Nutrition, Insulet, LifeScan, Medtronic Diabetes, Nipro Home Diagnostics, Nova Diabetes Care, Omron, Perrigo Diabetes Care, Roche Diabetes Care, and Sanofi Aventis.
Reference: DCCT/EDIC Research Group, Nathan DM, Bebu I, Hainsworth D, et al. Frequency of evidence-based screening for retinopathy in type 1 diabetes. N Engl J Med. 2017;376:1507-1516.