title: Is the PANSS used correctly? a systematic review.
abstract: BACKGROUND
  The PANSS (Positive and Negative Syndrome Scale) is one of the most important rating instruments for patients with schizophrenia. Nevertheless, there is a long and ongoing debate in the psychiatric community regarding its mathematical properties.All 30 items range from 1 to 7 leading to a minimum total score of 30, implying that the PANSS is an interval scale. For such interval scales straightforward calculation of relative changes is not appropriate. To calculate outcome criteria based on a percent change as, e.g., the widely accepted response criterion, the scale has to be transformed into a ratio scale beforehand. Recent publications have already pointed out the pitfall that ignoring the scale level (interval vs. ratio scale) leads to a set of mathematical problems, potentially resulting in erroneous results concerning the efficacy of the treatment.
  
  
  METHODS
  A Pubmed search based on the PRISMA statement of the highest-ranked psychiatric journals (search terms "PANSS" and "response") was carried out. All articles containing percent changes were included and methods of percent change calculation were analysed.
  
  
  RESULTS
  This systematic literature research shows that the majority of authors (62%) actually appear to use incorrect calculations. In most instances the method of calculation was not described in the manuscript.
  
  
  CONCLUSIONS
  These alarming results underline the need for standardized procedures for PANSS calculations.
authors.affiliation: Department of Psychiatry and Psychotherapy, Ludwig-Maximilians-University Munich, Nussbaumstrasse 7, Munich, Germany. Michael.Obermeier@med.uni-muenchen.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Obermeier
authors.forename: Rebecca
authors.initials: R
authors.lastname: Schennach-Wolff
authors.forename: Sebastian
authors.initials: S
authors.lastname: Meyer
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Möller
authors.forename: Michael
authors.initials: M
authors.lastname: Riedel
authors.forename: Daniela
authors.initials: D
authors.lastname: Krause
authors.forename: Florian
authors.initials: F
authors.lastname: Seemüller
mesh_terms: D006801:Humans; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data*; D012559:Schizophrenia / Q000175:diagnosis*