title: Equipercentile linking of scales measuring functioning and symptoms: examining the GAF, SOFAS, CGI-S, and PANSS.
abstract: The Global Assessment of Functioning (GAF) and the Social and Occupational Functioning Assessment Scale (SOFAS) are rating scales commonly used to assess the level of functioning in patients with schizophrenia. To understand the correspondence of scores between GAF and SOFAS, and what they mean from a clinical point of view, we examined the linkage of (a) GAF with SOFAS total scores, (b) GAF with Clinical Global Impressions Scale (CGI) and Positive and Negative Syndrome Scale (PANSS), and (c) SOFAS with CGI and PANSS. We used the equipercentile linking method to identify corresponding scores of simultaneous GAF, SOFAS, PANSS and CGI ratings in 1208 patients from a naturalistic European cohort study. Data were collected at baseline and at months 6, 12, 18 and 24. GAF and SOFAS total scores were found to be practically exchangeable. Both scales had strong negative correlations with CGI and PANSS; the linkage also suggested the presence of slight impairment in functioning even when patients are free from symptoms. These findings are important for the comparison of scores when different rating scales are used. We present a detailed conversion table in an online supplement.
authors.affiliation: Department of Psychiatry and Psychotherapy, Technische Universität München, Klinikum rechts der Isar, Ismaningerstr. 22, 81675 Munich, Germany.
authors.forename: Myrto T
authors.initials: MT
authors.lastname: Samara
authors.affiliation: Psychiatrische Klinik der Ludwig-Maximilian-Universität München, Nussbaumstrasse 7, 80336 Munich, Germany.
authors.forename: Rolf R
authors.initials: RR
authors.lastname: Engel
authors.affiliation: Creativ-Ceutical, 215 rue du Faubourg St-Honoré, 75008 Paris, France.
authors.forename: Aurelie
authors.initials: A
authors.lastname: Millier
authors.affiliation: Medical Therapeutic Area Lead Neuroscience and Rheumatology, Roche Pharma AG, Medical Management Specialty Care, Emil-Barell-Str.1, 79639 Grenzach-Wyhlen, Bau 200, 3-N.10, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Kandenwein
authors.affiliation: Aix Marseille University, Faculté de Médecine, Laboratoire de Santé Publique, 27 bd Jean Moulin, 13385 Marseille Cedex 05, France.
authors.forename: Mondher
authors.initials: M
authors.lastname: Toumi
authors.affiliation: Department of Psychiatry and Psychotherapy, Technische Universität München, Klinikum rechts der Isar, Ismaningerstr. 22, 81675 Munich, Germany. Electronic address: Stefan.Leucht@lrz.tum.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Leucht
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D012559:Schizophrenia / Q000175:diagnosis*; D055815:Young Adult
keywords: Equipercentile; Functioning; GAF; Linking; SOFAS; Schizophrenia