Dissemination in space is one of two conceptional columns on which consensus diagnostic criteria of multiple sclerosis (MS) rests. Consistently cross-sectional data has demonstrated that optical coherence tomography (OCT) can be used to reveal the inter-eye difference of retinal layers as an additional para-clinical test in this context.
To test the validity of the inter-eye difference of retinal layers as a diagnostic test in multiple sclerosis longitudinally.
Patients with multiple sclerosis and healthy controls who were longitudinally followed up at the Multiple Sclerosis Centre Amsterdam underwent OCT assessment at baseline and two year follow-up. We calculated the inter-eye percentage difference (IEPD) for the macular ganglion-cell inner plexiform layer (mGCIPL). Previously published cut-off levels (IMSVISUAL) were used to calculate diagnostic sensitivity and specificity levels.
We included 199 participants of which 39 were healthy controls (HC). Patients with multiple sclerosis either had never experienced a clinical attack of optic neuritis (Non-MSON, n=81), suffered from unilateral MSON (n=48) or bilateral MSON (n=31). Longitudinal progression on the EDSS was less marked in these groups compared to longitudinal progression of mGCIPL atrophy. At baseline the diagnostic sensitivity and specificity values for the IEPD of the mGCIPL for comparing HC with unilateral MSON were 70%/97%, and with bilateral MSON 86%/97%. At two year follow-up the respective diagnostic sensitivity and specificity levels were 71%/97% and 83%/97%.
The inter-eye difference of the mGCIPL could be validated as a robust para-clinical test for multiple sclerosis longitudinally. These data were based on presence of a clinical episode of either unilateral or bilateral MSON. Extension of this approach to consider asymptomatic optic nerve pathology is warranted to further increase diagnostic sensitivity levels.