International Journal of Preventive Medicine (Int J Prev Med)2008-78021120110713232232ENMD, Resident of Ophtalmology,Medical School, Isfahan University of Medical Sciences, Isfahan, Iran; Department of Ophtalmology, Feiz eye Hospital, Isfahan University of Medical Sciences, Isfahan, Iran.Professor of Ophtalmology,Medical School, Isfahan University of Medical Sciences, Isfahan, Iran; Department of Ophtalmology, Feiz eye Hospital, Isfahan University of Medical Sciences, Isfahan, Iran.Student of Medicine, Medical Researcher, Isfahan Research Committee of Multiple Sclerosis (IRCOMS), Isfahan, Iran. Medical School, Isfahan University of Medical Sciences, Isfahan, Iran. Isfahan Medical Students Research Committee (IMSRC), Isfahan, Iran.Medical School, Isfahan University of Medical Sciences, Isfahan, Iran Department of Ophtalmology, Feiz eye Hospital, Isfahan University of Medical Sciences, Isfahan, IranMedical School, Department of Ophtalmology, Feiz Eye Hospital, Isfahan University of Medical Sciences, Isfahan, IranEpidemiologist, Department of Epidemiology and Statistics, Isfahan University of Medical Sciences, Isfahan, Iran.Assistant Professor of Neurology, Hamadan University of Medical Sciences, Hamadan, Iran.MD, Medical Researcher,Isfahan Research Committee of Multiple Sclerosis (IRCOMS), Isfahan, Iran. Medical School, Isfahan University of Medical Sciences, Isfahan, Iran. Neuroimmunology unit, Centre for Neuroscience & Trauma, Blizard Institute of Cell and Molecular Science, Barts and the London School of Medicine and Dentistry, London, UK.2011062520110712<p><strong>Background: </strong>Optic neuritis (ON) can be the first presentation of multiple sclerosis (MS) or neuromyelitis optica (NMO). Antiaquaporin-4 IgG (AQP4 IgG) is a highly specific and moderately sensitive biomarker for NMO. This study was designed to assess the rate of seropositivity for AQP4 IgG, and the short-term outcome of patients presenting with single isolated ON (SION).</p> <p><strong>Methods: </strong>A cohort of 41 consecutive patients experiencing severe (&lt; 20 / 200) SION (not fulfilling the diagnostic criteria for MS or NMO), was prospectively recruited. Blood sampling was carried out immediately after the diagnosis of ON, and AQP4 IgG was tested qualitatively, using an indirect immunofluorescence kit. After clinical and paraclinical investigations, all the patients were followed up for a short-term period of at least 18 months.</p> <p><strong>Results: </strong>The seroprevalence among the initial ON patients was 9.7% (4 / 41). The short-term conversion rate to MS and NMO was estimated to be about 7.3 and 4.9%, respectively. The conversion rate to NMO in initially seropositive patients was greater than that for the whole cohort [2 / 4 (50%) vs. 2 / 41 (4.9%); <em>P </em>= 0.035; Odds ratio: 19.5, 95% confidence interval: 1.73 to 219.50].</p> <p><strong>Conclusion: </strong>AQP4 IgG seropositive SION patients were more likely to develop NMO in comparison to the total SION population. Further studies, with a longer follow-up period and larger sample sizes are warranted to assess the clinical and prognostic value of assessing AQP4 IgG in SION.</p> <strong>Key words: </strong>Anti aquaporin-4 IgG, Iran, Isfahan, multiple sclerosis, neuromyelitis optica, optic neuritishttp://ijpm.mui.ac.ir/index.php/ijpm/article/view/232http://ijpm.mui.ac.ir/index.php/ijpm/article/download/232/644