Optimal frequency of retinopathy screening in adolescents with type 1 diabetes - Markov modelling approach based on 30-years of data

Background: Current guidelines recommend biennial diabetic retinopathy (DR) screening commencing at age of 11years and after 2-5 years duration of type 1 diabetes. Growing evidence suggests less frequent screening may be feasible. 

Methods: Prospective data were collected from 2,063 youth with type 1 diabetes who were screened ≥2 times between 1990-2019. Baseline (mean±SD) age was 13.3±1.8 years, HbA1c 8.6±1.3% (70.1±14.7 mmol/mol), diabetes duration 5.6±2.8 years and follow-up time 4.8±2.8 years. DR was manually graded from 7-field retinal photographs using the ETDRS scale. Markov chain was used to calculate probabilities of DR change over time and hazard ratio (HR) of DR stage transition. 

Results: The incidence of moderate non-proliferative DR (MNPDR) or worse was 8.6 per 1000 patient years. Probabilities of transition to this state after 3- years interval were: from no-DR 1.3%; from minimal DR 5.1%; from mild DR 22.2% respectively. HRs (95%CI) for transition per 1% current HbA1c increase were: 1.23 (1.16-1.31) from no-DR to minimal NPDR, 1.12 (1.03-1.23) from minimal to mild NPDR, 1.28 (1.13-1.46) from mild to MNPDR or worse. HbA1c alone explained 27% of the transitions between no-retinopathy and MNPDR or worse. The addition of diabetes duration into the model increased this value to 31% (p=0.03). Risk was also increased by female sex, and higher attained age. 

Conclusions: These results support less frequent DR screening in youth with type 1 diabetes without DR and short duration. Although DR progression to advanced stages is generally slow, higher HbA1c greatly accelerates it.