title: A study of the dimensionality and measurement precision of the SCL-90-R using item response theory.
abstract: We used item response theory (IRT) to (a) investigate the dimensionality of the Symptom Checklist-90-Revised (SCL-90-R) in a severely disturbed patient group, (b) improve the subscales in a meaningful way and (c) investigate the measurement precision of the improved scales. The total sample comprised 3078 patients (72% women, mean age=35±9) admitted to 14 different day hospitals participating in the Norwegian Network of Personality-focused Treatment Programmes. Mokken Scale Analysis was used to investigate the dimensionality of the SCL-90-R and improve the subscales. This analysis was theory-driven: the scales were built on two start items that reflected the content of the disorder that corresponds with the specific scale. The Graded Response Model was employed to determine measurement precision. Our theory-driven IRT approach resulted in a new seven-factor solution including 60 of the 90 items clustered in seven scales: depression, agoraphobia, physical complaints, obsessive-compulsive, hostility (unchanged), distrust and psychoticism. Most of the new scales discriminated reliably between patients with moderately low scores to moderately high scores. In conclusion, we found support for the multidimensionality of the SCL-90-R in a large sample of severely disturbed patients.
authors.affiliation: Department of Neuropsychiatry and Psychosomatic Medicine, Oslo University Hospital, and Institute of Clinical Medicine, University of Oslo, Oslo, Norway. muirne@nxdomain.nl
authors.forename: Muirne C S
authors.initials: MC
authors.lastname: Paap
authors.forename: Rob R
authors.initials: RR
authors.lastname: Meijer
authors.forename: Jan
authors.initials: J
authors.lastname: Van Bebber
authors.forename: Geir
authors.initials: G
authors.lastname: Pedersen
authors.forename: Sigmund
authors.initials: S
authors.lastname: Karterud
authors.forename: Frøydis M
authors.initials: FM
authors.lastname: Hellem
authors.forename: Ira R
authors.initials: IR
authors.lastname: Haraldsen
mesh_terms: D000328:Adult; D003863:Depression / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis* / Q000453:epidemiology; D009664:Norway / Q000453:epidemiology; D010554:Personality Disorders / Q000175:diagnosis* / Q000453:epidemiology* / Q000523:psychology; D010555:Personality Inventory; D011582:Psychological Theory; D011594:Psychometrics; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires