Corneal Confocal Microscopy Predicts the Development of Diabetic Neuropathy: A Longitudinal Diagnostic Multinational Consortium Study

Objectives: Corneal nerve fiber length (CNFL) has been shown in research studies to identify diabetic peripheral neuropathy (DPN). In this longitudinal diagnostic study, we assessed the ability of CNFL to predict the development of DPN.

Research Design and Methods: From a multinational cohort of 998 participants with type 1 and type 2 diabetes, we studied the subset of 261 who were free of DPN at baseline and completed at least four years of follow-up for incident DPN. The predictive validity of CNFL for the development of DPN was determined using time-dependent receiver operating characteristic (ROC) curves.

Results: 203 participants had type 1 and 58 had type 2 diabetes. Mean follow-up time was 5.8 years (interquartile range 4.2-7.0). New onset DPN occurred in 60 participants (23%; 4.29 events per 100 person years). Participants who developed DPN were older, had a higher prevalence of type 2 diabetes, higher BMI, and longer duration of diabetes. The baseline electrophysiology and CCM parameters were in the normal range but were all significantly lower in participants who developed DPN. The time-dependent area under the ROC curve (AUC) for CNFL ranged between 0.61 and 0.69 for years 1-5 and was 0.80 at year 6. The optimal diagnostic threshold for a baseline CNFL of 14.1mm/mm² was associated with 67% sensitivity, 71% specificity, and a hazard rate ratio of 2.95 (95% CI 1.70-5.11, p<0.001) for new onset DPN.

Conclusions: CNFL showed good predictive validity for identifying patients at higher risk of developing DPN approximately 6 years in the future.