DCCT data refine retinopathy screening intervals
medwireNews: Researchers have used DCCT/EDIC data to produce risk-based screening recommendations for retinopathy in patients with type 1 diabetes that reduce costs without delaying diagnosis.
The recommendations are based on just two factors: current retinopathy stage and average glycated hemoglobin (HbA1c) levels. Using these, John Lachin (George Washington University, Rockville, Maryland, USA) and team were able to determine screening intervals that left patients with around a 5% risk for progression to stage 5 retinopathy (proliferative diabetic retinopathy or clinically significant macular edema) between eye examinations.
Their conclusions are based on an average 23.5 years’ follow-up of 1375 participants of DCCT and its observational follow-up study EDIC.
The team proposes a “practical schedule” using screening intervals of 4 years, 3 years, 6 months, and 3 months for patients with stage 1, 2, 3, and 4 retinopathy, respectively. This is based on progression rates to stage 5 of 2.9%, 3.7%, 6.6%, and 14.4% for patients with the respective retinopathy stages during these time intervals.
Reducing progression risk to around 5% for patients with stage 4 retinopathy would require monthly screening (5.7% risk).
Although various patient factors such as age, diabetes duration, and body mass index were also associated with retinopathy progression risk, only HbA1c had “a substantive effect.” For example, the recommended screening interval for patients with stage 2 retinopathy was 3 years, but for patients with HbA1c levels of 6% and 8%, this could be increased to 5 and 4 years, respectively, at progression risks of 1.9% and 4.4%. But for those with an HbA1c of 10%, the screening interval had to be reduced to 2 years to achieve an acceptable progression risk, of 4.5%.
The recommended screening intervals were similar whether based on updated average or current HbA1c levels, the researchers note in The New England Journal of Medicine.
Lachin et al have produced a web application that generates recommended screening intervals based on a patient’s retinopathy stage and HbA1c level, available here. They calculate that, over a 20-year period, their approach would result in a 58% reduction in the number of required eye examinations per patient, with resultant large cost savings.
In an accompanying editorial, Jamie Rosenberg (Montefiore Medical Center, New York, USA) and Irena Tsui (University of California, Los Angeles, USA) note that such savings would need to be demonstrated in a formal cost-effectiveness analysis, but say that the approach “could be a step forward in detecting diabetic retinopathy.”
However, the editorialists say that one stumbling block could be the increased complexity of the approach. They observe that, in the real world, primary care providers and endocrinologists, rather than ophthalmologists, are largely responsible for ensuring patients undergo regular eye examinations, and that complicating the process could further reduce their already low referral rates.
They also note that the expanding indications for anti-vascular endothelial growth factor intravitreal injections may ultimately require a different approach to screening, “with broader use of advanced retinal imaging to detect retinal nonperfusion that is amenable to treatment.”
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