title: Use of non-parametric item response theory to develop a shortened version of the Positive and Negative Syndrome Scale (PANSS).
abstract: BACKGROUND
  Nonparametric item response theory (IRT) was used to examine (a) the performance of the 30 Positive and Negative Syndrome Scale (PANSS) items and their options ((levels of severity), (b) the effectiveness of various subscales to discriminate among differences in symptom severity, and (c) the development of an abbreviated PANSS (Mini-PANSS) based on IRT and a method to link scores to the original PANSS.
  
  
  METHODS
  Baseline PANSS scores from 7,187 patients with Schizophrenia or Schizoaffective disorder who were enrolled between 1995 and 2005 in psychopharmacology trials were obtained. Option characteristic curves (OCCs) and Item Characteristic Curves (ICCs) were constructed to examine the probability of rating each of seven options within each of 30 PANSS items as a function of subscale severity, and summed-score linking was applied to items selected for the Mini-PANSS.
  
  
  RESULTS
  The majority of items forming the Positive and Negative subscales (i.e. 19 items) performed very well and discriminate better along symptom severity compared to the General Psychopathology subscale. Six of the seven Positive Symptom items, six of the seven Negative Symptom items, and seven out of the 16 General Psychopathology items were retained for inclusion in the Mini-PANSS. Summed score linking and linear interpolation was able to produce a translation table for comparing total subscale scores of the Mini-PANSS to total subscale scores on the original PANSS. Results show scores on the subscales of the Mini-PANSS can be linked to scores on the original PANSS subscales, with very little bias.
  
  
  CONCLUSIONS
  The study demonstrated the utility of non-parametric IRT in examining the item properties of the PANSS and to allow selection of items for an abbreviated PANSS scale. The comparisons between the 30-item PANSS and the Mini-PANSS revealed that the shorter version is comparable to the 30-item PANSS, but when applying IRT, the Mini-PANSS is also a good indicator of illness severity.
authors.affiliation: Fordham University, Department of Psychometrics, Bronx, NY, USA. akhan@nki.rfmh.org
authors.forename: Anzalee
authors.initials: A
authors.lastname: Khan
authors.forename: Charles
authors.initials: C
authors.lastname: Lewis
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Lindenmayer
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000175:diagnosis*; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000175:diagnosis*; D012720:Severity of Illness Index
references.citation: Med Care. 2000 Sep;38(9 Suppl):II66-72
references.pmid: 10982091
references.citation: J Nerv Ment Dis. 1994 Nov;182(11):631-8
references.pmid: 7964671
references.citation: Schizophr Bull. 1987;13(2):261-76
references.pmid: 3616518
references.citation: J Appl Meas. 2002;3(2):205-31
references.pmid: 12011501
references.citation: Schizophr Res. 2006 Feb 28;82(2-3):213-23
references.pmid: 16229988
references.citation: Psychol Assess. 2000 Sep;12(3):354-9
references.pmid: 11021160
references.citation: Schizophr Res. 2008 Jan;98(1-3):318-22
references.pmid: 17949948
references.citation: Psychiatry Res. 2011 Aug 15;188(3):446-52
references.pmid: 21463902
references.citation: Qual Life Res. 2007;16 Suppl 1:85-94
references.pmid: 17286198
references.citation: Qual Life Res. 2004 Dec;13(10):1683-97
references.pmid: 15651539
references.citation: Schizophr Res. 2005 Jan 1;72(2-3):123-9
references.pmid: 15560957
references.citation: Psychiatr Clin North Am. 2007 Sep;30(3):339-63
references.pmid: 17720027
references.citation: J Clin Epidemiol. 1997 Mar;50(3):247-52
references.pmid: 9120523
references.citation: Compr Psychiatry. 1986 Jul-Aug;27(4):276-86
references.pmid: 3731764
references.citation: BMC Psychiatry. 2007 Nov 15;7:66
references.pmid: 18005449
references.citation: Acta Psychiatr Scand. 1986 Nov;74(5):507-18
references.pmid: 3492863
references.citation: BMC Psychiatry. 2011 Jul 18;11:113
references.pmid: 21767349
references.citation: Psychiatry Res. 1988 Jan;23(1):99-110
references.pmid: 3363019
references.citation: Psychiatry Res. 1994 Jul;53(1):31-40
references.pmid: 7991730
references.citation: Psychol Assess. 2001 Mar;13(1):127-39
references.pmid: 11281034