Individualised screening for diabetic retinopathy with proliferative retinopathy and macular oedema as separate end points.

Purpose: A number of algorithms have been developed to calculate screening intervals for diabetic retinopathy on the basis of individual risk factors. However, these approaches have not considered proliferative diabetic retinopathy (PDR) and diabetic macular oedema (DME) as separate end points and death as competing risk.

Methods: A multi-state survival model with death as competing risk was used to predict the screening interval for diabetic retinopathy based on information about all 2446 patients from a well-defined population who had started treatment for either PDR or DME during 25 years. The performance of the model was tested on the existing database and at seven screening sites on patients who had not developed a treatment requiring condition.

Results: Testing on the existing database showed that at a risk level of 2% the algorithm could predict a screening interval with a success rate higher than 90% and a 1.75 times average prolongation of the screening interval without failing to detect the development of verified PDR og DME. The model was limited to a diabetes duration shorter than 40 years and depended on knowledge of relevant risk factors. At the other participating screening sites the algorithm predicted shorter intervals than the screener.

Conclusions: Algorithms for individualised screening for diabetic retinopathy can prolong screening intervals without losing patients who develop a vision threatening condition. The calculation of screening intervals requires access to relevant risk factors and should be developed on large data sets that reflect the population in which the algorithm should be used.