Diagnostic value of corneal confocal microscopy in diabetic peripheral neuropathy of type 2 diabetes mellitus

Abstract

Objective To investigate the diagnostic value of corneal confocal microscopy in diabetic peripheral neuropathy (DPN) and the best diagnostic cut-off point in type 2 diabetes. Methods From September 2015 to February 2016, a total of 95 inpatients with type 2 diabetes were enrolled, including 56 males and 39 females, mean age (57±14) yrs. All the subjects were divided into DPN group and non-DPN group according to nerve conduction velocity(NCV), and received in vivo corneal confocal microscope examination(IVCCM). The corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length(CNFL) were recorded. The correlations between corneal nerve parameters and NCVs were analyzed. Receiver operating characteristic(ROC) curve was used for assessment of the values of corneal nerve parameters in diagnosis of DPN and finding best diagnostic cut-off point. Results The values of corneal nerve parameters in DPN group were significantly decreased than those in non-DPN group. The values of CNFD, CNBD, CNFL were positively correlated with motor nerve conduction velocity of median nerve, tibial nerve and peroneal nerve (r= 0.348-0.453, all P<0.01), and also positively correlated with sensory nerve conduction velocity of all the sensory nerve(r=0.203-0.478, all P<0.05). The areas under curve(AUC) in ROC curve of CNFD, CNBD and CNFL were among 0.7-0.9. In consistency test, Kappa value of CNFL was the highest. Taking CNFL≤20.6 mm/mm2 as the diagnostic cut-off point for DPN got the better sensitivity(82.4%) and specificity (85.7%). Conclusion IVCCM has a certain diagnostic value in diagnosis of DPN of type 2diobetes. CNFL≤20.6 mm/mm2 as the diagnostic cut-off point for DPN may have better sensitivity and specificity. Key words: Diabetes mellitus, type 2; Peripheral nervous system diseases; Cornea; ROC curve