In vivo corneal confocal microscopy and prediction of future-incident neuropathy in type 1 diabetes: a preliminary longitudinal analysis

Objective: In vivo corneal confocal microscopy (IVCCM) has been established in cross-sectional studies as a valid measure for the identification of diabetic sensorimotor polyneuropathy (DSP). We aimed to determine the predictive validity of a baseline IVCCM measure in identifying future DSP onset in patients with type 1 diabetes.

Methods: We followed 65 patients with type 1 diabetes without DSP at baseline. They were followed longitudinally for a mean of 3.5±0.9 years and underwent IVCCM, clinical and electrophysiologic examinations at baseline and follow up. At the end of follow up, participants were assigned as new-onset cases of DSP or as controls. Predictive validity was assessed using receiver operating characteristic curves.

Results: At baseline, participants were 34±15 years of age with mean diabetes duration of 18±12 years. The 11 (17%) new-onset cases of DSP were similar to the 54 (83%) controls in baseline age, diabetes duration, gender, glycated hemoglobin levels and electrophysiologic parameters (p≥0.20). However, cases of new onset had significantly lower baseline corneal nerve fibre length (CNFL) and branch density (p<0.05). For identification of new-onset cases, area under the receiver operating characteristic curve for CNFL was 0.78 with an optimal threshold of 14.9 mm/mm(2) (sensitivity=0.82, specificity=0.69).

Conclusions: Despite similar clinical and electrophysiologic parameters, participants with type 1 diabetes at risk for future DSP had significantly lower baseline IVCCM measures. CNFL may have applicability in identifying high-risk patients for therapeutic intervention in clinical research and practice.