Regular Article Psychother Psychosom 1998;67:17–23 Psychometric Characteristics of the Somatoform Dissociation Questionnaire: A Replication Study 1 Ellert R.S. Nijenhuis a, b Philip Spinhoven c Richard van Dyck a Onno van der Hart d Johan Vanderlinden e a Department of Psychiatry Vrije Universiteit at Amsterdam, b Outpatient Department General Psychiatric Hospital Drenthe, Assen, c Department of Psychiatry, Leiden University, d Department of Clinical Psychology and Health Psychology, Utrecht University, The Netherlands; e University Center St-Jozef, Kortenberg, Belgium OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO Key Words Dissociation Somatoform dissociation Dissociative disorders Measurement Self-report questionnaire Screening instrument OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO Abstract Background: The present study aimed to replicate the results of previous studies concerning the development of two versions of the Somatoform Disso- ciation Questionnaire. The SDQ-20 evaluates the severity of somatoform dis- sociative phenomena, and the SDQ-5 is a dissociative disorders screening instrument. Methods: Thirty-one patients with dissociative disorders and 45 consecutive psychiatric outpatients with other DSM-IV diagnoses completed the SDQ-20 and SDQ-5 as well as the Dissociation Questionnaire which mea- sures psychological dissociation. Results: Mokken scale analysis showed that the items of the SDQ-20 are strongly scalable on a latent unidimensional scale. Internal consistency was high. The SDQ-20 convergent validity was supported by high intercorrelations with the DIS-Q. Dissociative patients obtained sig- nificantly higher scores than comparison patients. Patients with dissociative identity disorder scored significantly higher compared to patients with disso- ciative disorder nos. Sensitivity (94%) and specificity (98%) of the SDQ-5 were very satisfactory, as were, at an estimated prevalence rate of dissociative disorders of 10% among psychiatric patients, positive predictive value (84%) and negative predictive value (99%). Conclusions: All results replicated the first findings, and therefore corroborate the conclusion that the SDQ-20 and SDQ-5 are instruments of sound psychometric quality, and that somatoform dissociative phenomena are core symptoms of complex dissociative disor- ders. OOOOOOOOOOOOOOOOOOOOOO E.R.S. Nijenhuis Department of Psychiatry, Vrije Universiteit Amsterdam Valeriusplein 9 NL–1075 BG Amsterdam (The Netherlands) Tel. 592334120, Fax 592334179 ABC Fax + 41 61 306 12 34 E-Mail karger@karger.ch www.karger.com © 1998 S. Karger AG, Basel 0033–3190/98/0671–0017$15.00/0 This article is also accessible online at: http://BioMedNet.com/karger Introduction According to DSM-IV [1], the essential feature of dis- sociative disorders is a disruption of the usually inte- grated functions of memory, consciousness, identity and perception. This definition ignores that the body and bodily functions may also be subject to dissociation. Clin- ical observations, however, confirm the view prevailing in 19th century French psychiatry that somatoform symp- toms may constitute somatic manifestations of dissocia- tion [2–8]. Examples include kinesthetic and visual anes- thesia, motoric inhibitions, intermittent pain symptoms, 1 Supported by a grant of the Stichting Dienstbetoon Gezondheidszorg, Soesterberg, The Netherlands. Grantnumber: LK 11.92. Downloaded by: KU Leuven University Library 134.58.253.30 - 5/13/2015 1:42:23 PM