Psychometric characteristics of the somatoform dissociation questionnaire: a replication study.
BACKGROUND
The present study aimed to replicate the results of previous studies concerning the development of two versions of the Somatoform Dissociation Questionnaire. The SDQ-20 evaluates the severity of somatoform dissociative 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 measures 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 significantly higher scores than comparison patients. Patients with dissociative identity disorder scored significantly higher compared to patients with dissociative 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 disorders.
Nijenhuis
E R
ER
Department of Psychiatry Vrije Universiteit at Amsterdam, The Netherlands.
Spinhoven
P
P
van Dyck
R
R
van der Hart
O
O
Vanderlinden
J
J
D000293:Adolescent; D000328:Adult; D004213:Dissociative Disorders / Q000145:classification / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000523:psychology; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales / Q000592:standards*; D015203:Reproducibility of Results; D012647:Self-Assessment; D012720:Severity of Illness Index