Background:The presence of a ‘fog’ is frequently reported by patients with systemic lupus erythematosus (SLE). However, little is known about this lupus fog: it is thought to be a result of cognitive dysfunction, but fogs can also be the result of dissociation. The Dissociative Experience Scale-II (DES) is a standardized tool to study dissociation. In the general adult population, scores range from 4.4-14.1-3Objectives:We aimed to study the prevalence of dissociative symptoms including dissociative fog in patients with SLE and neuropsychiatric symptoms.Methods:Patients visiting the tertiary referral center for neuropsychiatric systemic lupus erythematosus (NPSLE) of the LUMC between 2007-2019 were included. All patients underwent a standardized multidisciplinary assessment. Patients were classified as NPSLE if neuropsychiatric symptoms were attributed to SLE and immunosuppressive or anticoagulant therapy was initiated, otherwise patients were classified as minor/non-NPSLE. Dissociation was studied using the DES. The DES separates different types of dissociative symptoms: amnesia, absorption/imagination and derealization/depersonalization. It also contains one question regarding evaluating the presence of a dissociative fog: “Some people sometimes feel as if they are looking at the world through a fog, so that people and objects appear far away or unclear”. All statements (n = 28) regarding dissociative symptoms are rated from ‘none of the time’ to ‘all of the time’ (0-100%); scores >25 are considered abnormal. A multiple regression analysis (MRA) were performed to compare dissociation in patients with and without NPSLE. DES results are presented as median (range) and MRA as odds ratio (OR) and 95% confidence interval (CI).Results:DES questionnaires were available for 337 patients, of which 97 had the diagnosis NPSLE (29%). Mean age in patients with NPSLE was 41 ± 13 years and 84% was female. In minor/non-NPSLE, median age was 44 ± 14 years and 87% was female.Median dissociation was 7 (0-75) and did not differ between patients with minor/non-NPSLE and NPSLE (OR: 1.0 (95% CI: -0.9; 1.1)). The most common type of dissociation was absorption/imagination (median: 12, range 0-75) and depersonalization/derealization was infrequent (median: 1, range 0-84). 43 patients (13%) had an abnormal score (>25) on the dissociative fog question.Conclusion:Dissociative symptoms are within normal range in patients with SLE and neuropsychiatric symptoms, regardless of underlying etiology. Dissociative fog seems uncommon and therefore lupus fog is most likely not the result of dissociation.References:[1]Bernstein EM and Putnam FW. Development, reliability, and validity of a dissociation scale. J Nerv Ment Dis 1986; 174: 727-735. 1986/12/01. DOI: 10.1097/00005053-198612000-00004.[2]Maaranen P, Tanskanen A, Honkalampi K, et al. Factors associated with pathological dissociation in the general population. Aust N Z J Psychiatry 2005; 39: 387-394. 2005/04/30. DOI: 10.1080/j.1440-1614.2005.01586.x.[3]van IJzendoorn MH and Schuengel C. The measurement of dissociation in normal and clinical populations: Meta-analytic validation of the Dissociative Experiences Scale (DES). Clinical Psychology Review 1996; 16: 365-382. DOI: 10.1016/0272-7358(96)00006-2.Table 1.Presence of dissociation in patients with SLE and neuropsychiatric symptomsTotal cohort(n = 337)Minor/non-NPSLE(n = 240)NPSLE(n = 97)DES (median, range)Total questionnaire7 (0 - 75)8 (0 - 66)6 (0 – 75)Amnesia5 (0 - 76)5 (0 - 68)4 (0 - 76)Absorption/imagination12 (0 – 75)13 (0 – 75)10 (0 – 73)Depersonalization/derealization1 (0 – 84)1 (0 – 73)1 (0 – 84)Dissociative fog* 0 (0-100)0 (0-100)0 (0-100)DES = Dissociative Experience Scale NPSLE = neuropsychiatric systemic lupus erythematosus.*Dissociative fog is question 28 of the DES-IIDisclosure of Interests:None declared