Corneal confocal microscopy adequate for DPN detection in T2DM
Corneal confocal microscopy (CCM) may help detect diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes mellitus (T2DM), a recent study has found.
The study included 220 participants, of whom 172 had T2DM, and the other 48 were set as healthy controls. Aside from CCM, the Diabetic Neuropathy Syndrome (DNS), Neurological Deficit Score (NDS), and neuroelectrophysiological and quantitative sensory testing were all also performed for DPN assessment.
Relative to controls, the NDS and DNS scores were significantly higher in T2DM patients, as were the warm sensation and vibration perception thresholds. The cold sensation threshold, on the other hand, was lower in T2DM patients (p<0.001 for all). Using the Toronto Diabetic Neuropathy Expert Group recommendation, 100 T2DM patients were identified to have DPN.
CCM parameters differed significantly between DPN and non-DPN participants. For example, mean corneal nerve fibre density (CNFD) was significantly higher among those without DPN (23.27±10.01 vs 17.67±7.95 n/mm2; p<0.001).
Similarly, corneal nerve branch density (CNBD; 37.38±17.76 vs 27.05±12.09 n/mm2; p<0.001) and corneal nerve fibre length (CNFL; 15.69±5.26 vs 12.56±3.80 n/mm2; p<0.001) were both significantly greater in non-DPN T2DM patients.
The researchers then performed receiver operating characteristic curve analysis to assess the value of CCM in diagnosing T2DM. At optimal CNFD, CNBD, and CNFL cut-off values of 22.125, 51.875, and 16.29 n/mm2, the areas under the curve (AUC) were 0.731, 0.7, and 0.27, respectively. CNFD and CNFL both had better sensitivity and specificity.
For DPN, the optimal cut-offs for CNFD, CNBD, and CNFL were 24.68, 39, and 15.315 nn/m2, at which values the AUCs were 0.668, 0.675, and 0.701, respectively.