The inter-eye percentage difference (IEPD) of the macular ganglion cell and inner plexiform layer (mGCIPL) as well as the IEPD of the peripapillary retinal nerve fiber layer (pRNFL) are practical diagnostic tools for multiple sclerosis (MS)-associated optic neuritis (MSON) and may surpass limitations associated with device and proprietary segmentation algorithms, according to a prospective, cross-sectional study published in the European Journal of Neurology.
Included in this study were patients with bilateral MSON (n=39) and unilateral MSON (n=62), patients without MSON (n=106), and healthy controls (n=63). The researchers performed spectral-domain optical coherence tomography in both eyes of the treatment patients. Afterward, the researchers also performed an automated retinal layer segmentation of the pRNFL and mGCIPL.
The diagnostic accuracy of the IEPD, represented by the area under the curve, was 0.75 to 0.94 for mGCIPL and 0.73 to 0.86 for pRNFL. Sensitivity of mGCIPL IEPD was found to be 70% and included a diagnostic specificity of 97% for differentiating healthy controls from unilateral MSON. Additionally, a sensitivity of 86% and specificity of 97% represented the comparison of healthy controls with bilateral MSON.
The investigators noted that the IEPD features a low diagnostic specificity in distinguishing MSON from other optic neuritis conditions that were not included in this study, representing a potential limitation to their findings.
However, the advantages of using the IEPD include “simplicity for clinical practice, the possibility to become a cross [optical coherence tomography] device measure, the suitability for many statistical models on established MS outcome measures, and a potentially robust and useful secondary outcome measure for treatment trials.”
Coric D, Balk LJ, Uitdehaag BMJ, Petzold A. Diagnostic accuracy of optical coherence tomography inter-eye percentage difference (IEPD) for optic neuritis in multiple sclerosis [published online September 8, 2017]. Eur J Neurol. doi: 10.1111/ene.13443