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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.

SUBMITTER: Khan A

PROVIDER: S-EPMC3256111 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Use of non-parametric item response theory to develop a shortened version of the Positive and Negative Syndrome Scale (PANSS).

Khan Anzalee A Lewis Charles C Lindenmayer Jean-Pierre JP

BMC psychiatry 20111116

<h4>Background</h4>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.<h4>Methods</h4>Baseline PANSS scores from 7,187 patients with Schizophrenia ...[more]

PMID: 22087503

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Project description:BackgroundStatistical models based on item response theory were used to examine (a) the performance of individual Positive and Negative Syndrome Scale (PANSS) items and their options, (b) the effectiveness of various subscales to discriminate among individual differences in symptom severity, and (c) the appropriateness of cutoff scores recently recommended by Andreasen and her colleagues (2005) to establish symptom remission.MethodsOption characteristic curves were estimated using a nonparametric item response model to examine the probability of endorsing each of 7 options within each of 30 PANSS items as a function of standardized, overall symptom severity. Our data were baseline PANSS scores from 9205 patients with schizophrenia or schizoaffective disorder who were enrolled between 1995 and 2003 in either a large, naturalistic, observational study or else in 1 of 12 randomized, double-blind, clinical trials comparing olanzapine to other antipsychotic drugs.ResultsOur analyses show that the majority of items forming the Positive and Negative subscales of the PANSS perform very well. We also identified key areas for improvement or revision in items and options within the General Psychopathology subscale. The Positive and Negative subscale scores are not only more discriminating of individual differences in symptom severity than the General Psychopathology subscale score, but are also more efficient on average than the 30-item total score. Of the 8 items recently recommended to establish symptom remission, 1 performed markedly different from the 7 others and should either be deleted or rescored requiring that patients achieve a lower score of 2 (rather than 3) to signal remission.ConclusionThis first item response analysis of the PANSS supports its sound psychometric properties; most PANSS items were either very good or good at assessing overall severity of illness. These analyses did identify some items which might be further improved for measuring individual severity differences or for defining remission thresholds. Findings also suggest that the Positive and Negative subscales are more sensitive to change than the PANSS total score and, thus, may constitute a "mini PANSS" that may be more reliable, require shorter administration and training time, and possibly reduce sample sizes needed for future research.

Project description:BackgroundThe investigation of patient-reported outcomes and psycho-oncological interventions mainly focuses on psychological distress or psychopathology. However, the recognition of the equal importance of positive mental health (PMH) has increased lately. The PMH-scale is a brief questionnaire allowing to assess well-being in individuals in the general population and in patients. Previous studies evaluated the psychometric properties of the PMH-scale using classical test theory (CTT). This study is the first to investigate the PMH-scale in patients with cancer using item analysis according to the Rasch model.MethodsIn total, N = 357 cancer patients participated in the study. A Rasch analysis of the PMH-scale was conducted including testing of unidimensionality, local independence, homogeneity and differential item functioning (DIF) with regard to age, gender, type of cancer, the presence of metastases, psycho-oncological support, and duration of disease. Additionally, the ordering of the item thresholds as well as the targeting of the scale were investigated.ResultsAfter excluding one misfitting item and accounting for local dependence by forming superitems, a satisfactory overall fit to the Rasch model was established (χ2 = 30.34, p = 0.21). The new PMH-8 scale proved to be unidimensional, and homogeneity of the scale could be inferred. All items showed ordered thresholds, there was no further item misfit. DIF was found for age, but as the impact of DIF was not substantial, no adjustment related to the age-DIF had to be made. The Person Separation Index (PSI = 0.89) was excellent, indicating excellent discriminatory power between different levels of positive mental health. Overall, the targeting of the PMH-8 was good for the majority of the present sample. However, at both ends of the scale item thresholds are missing as indicated by a slight floor effect (1.4%) and a considerable ceiling effect (9.8%).ConclusionsOverall, the results of the analysis according to the Rasch model support the use of the revised PMH-scale in a psycho-oncological context.

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Use of non-parametric item response theory to develop a shortened version of the Positive and Negative Syndrome Scale (PANSS).

Publications

Use of non-parametric item response theory to develop a shortened version of the Positive and Negative Syndrome Scale (PANSS).

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