Microscopic cornea exam could identify neuropathy risk in type 1 diabetes
SAN FRANCISCO — Diabetic sensorimotor polyneuropathy could be detected earlier in patients with type 1 diabetes through in vivo corneal confocal microscopy, according to research presented at the American Diabetes Association’s 74th Scientific Sessions.
“One of the big knowledge gaps in diabetes is we are quite good at screening for and identifying retinopathy and nephropathy, but we are terrible in clinical practice at being able to identify neuropathy until late stages when we’ve missed an opportunity to do something to prevent it,” Bruce Perkins, MD, MPH, FRCPC, of the University of Toronto, told Endocrine Today.
For the Toronto Longitudinal Neuropathy Cohort, funded by the Juvenile Diabetes Research Foundation, patients underwent annual in vivo corneal confocal microscopy (IVCCM) and full clinical and electrophysiological examinations for approximately 3.5 years. Perkins and colleagues looked at 102 patients with type 1 diabetes, with follow-up.
At baseline, 65 patients (64%; aged 34±15 years; diabetes duration, 18±12 years) without diabetic sensorimotor polyneuropathy (DSP) were assigned to a control group. At follow-up, 11 (17%) had developed new onset DSP and 54 (83%) remained as controls; those with new onset were similar in age, diabetes duration, sex, HbA1c and electrophysiological parameters.
The investigators used receiver operating characteristic curves to determine the predictive validity and role of IVCCM for type 1 diabetes.
Sural nerve amplitude potentials were 10.3±6.1µV at baseline for new onset and 12.5±4.9µV for control. Corneal nerve fiber length (CNFL) was significantly lower at baseline in new onset cases compared with controls (12.8±4.0 vs. 16.9±3.8 mm/mm2, P=.002), as was corneal nerve branch density (CNBD) (20.7±10.6 vs. 38.0±19.8 branches/mm2, P=.003).
CNFL had an AUC of 0.79 and an optimal threshold of 14.8 mm/mm2 (sensitivity=0.73, specificity=0.74) for predicting new onset. CNBD had an AUC of 0.77 and an optimal threshold of 30.6 branches/mm2 (sensitivity=0.73, specificity=0.61).
Despite similar clinical and electrophysiological parameters, the patients who were at risk for future onset of DSP demonstrated significantly lower IVCCM measures at baseline.
“Here’s an early marker that can tell us someone is starting along that pathway of injury to their nerves,” Perkins said.
The findings hold potential for clinical trials leading to better interventions to prevent the progression of nerve injury, as well for specialists to identify patients with early risk.
“Our vision is to harmonize this with the eye specialist exam that all patients with diabetes have every year anyway for their retina,” Perkins said. — by Allegra Tiver
For More Information: Perkins B. Abstract 117-OR. Presented at: American Diabetes Association’s 74th Scientific Sessions; June 13-17, 2014; San Francisco.
Disclosures: Perkins reports being a consultant for NeuroMetrix; receiving research support from Boehringer Ingelheim Pharmaceuticals, Inc. and Medtronic; being on the Speaker’s Bureau for GlaxoSmithKline, Johnson & Johnson, Metronic, Novo Nordisk, Inc., Roche Pharmaceuticals and Sanofi.