title: Should the PANSS be rescaled?
abstract: The design of the Positive and Negative Syndrome Scale (PANSS) with item levels ranging from 1 to 7 leads to the trivial result that the 30-item scale's zero level (no symptoms) is 30. This causes serious problems when ratios are calculated which always implicitly depend on a natural zero point (equals 0). Recent publications concerning efficacy of antipsychotics correctly suggest a subtraction of 30 points to every PANSS before calculating percent change (PC). Nevertheless, the traditional approach using uncorrected scores is still in common practice. This analysis aims to clarify which approach is the most appropriate from a statistical perspective.For analysis, data from a naturalistic study on 400 patients with a schizophrenic spectrum disorder and simulated data sets were used. While calculations concerning absolute score values and their differences are not affected, considerable problems arise in calculations of PC and related response criteria. Even significance levels of estimated treatment effects change, depending on the structure of the data (eg, baseline symptom severity). Using a PANSS version with items ranging from 0 to 6 would avoid such often neglected pitfalls.
authors.affiliation: Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University Munich, Nussbaumstrasse 7, 80336 Munich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Obermeier
authors.forename: Andreas
authors.initials: A
authors.lastname: Mayr
authors.forename: Rebecca
authors.initials: R
authors.lastname: Schennach-Wolff
authors.forename: Florian
authors.initials: F
authors.lastname: Seemüller
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Möller
authors.forename: Michael
authors.initials: M
authors.lastname: Riedel
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000627:therapeutic use; D015982:Bias; D002986:Clinical Trials as Topic / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data*; D011594:Psychometrics / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000175:diagnosis* / Q000188:drug therapy; D012565:Schizophrenic Psychology; D016896:Treatment Outcome
chemical_list: D014150:Antipsychotic Agents