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Item response analysis of the Positive and Negative Syndrome Scale.

Santor DA, Ascher-Svanum H, Lindenmayer JP, Obenchain RL - BMC Psychiatry (2007)

Bottom Line: Statistical 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Psychology, University of Ottawa, Ottawa, Canada, and The Provincial Centre of Excellence for Child and Youth Mental Health, Ottawa, Ontario, Canada. dsantor@uottawa.ca

ABSTRACT

Background: Statistical 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.

Methods: Option 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.

Results: Our 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.

Conclusion: This 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.

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Related in: MedlinePlus

Option characteristic curves and expected item total score for Item 1: Delusions. Option characteristic curves (solid lines) and expected item total score (dashed line) are plotted as a function of scores on the Positive Symptomatology Subscale form the PANNS, expressed as standard normal scores (lower x-axis) and expected total scores (upper x-axis). The probability of endorsing an option characteristic curve (solid lines) is scaled on the left y-axis and the expected item score (dashed line) is scaled on the right y-axis. Many features of an ideal item are evident in this plot.
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Figure 2: Option characteristic curves and expected item total score for Item 1: Delusions. Option characteristic curves (solid lines) and expected item total score (dashed line) are plotted as a function of scores on the Positive Symptomatology Subscale form the PANNS, expressed as standard normal scores (lower x-axis) and expected total scores (upper x-axis). The probability of endorsing an option characteristic curve (solid lines) is scaled on the left y-axis and the expected item score (dashed line) is scaled on the right y-axis. Many features of an ideal item are evident in this plot.

Mentions: Item 1, from the PANSS Positive Factor subscale, assesses suspiciousness, defined as "Beliefs which are unfounded, unrealistic, and idiosyncratic." Option characteristic curves for this item are presented in the second panel of Figure 2 and show that the probability of rating Option 1, assessing an "absence of symptoms," decreases rapidly as the severity of positive psychotic symptoms begins to increase. Meanwhile, the probability of endorsing the more severe levels of Delusions begins to increase rapidly with increases in the severity of positive symptoms.


Item response analysis of the Positive and Negative Syndrome Scale.

Santor DA, Ascher-Svanum H, Lindenmayer JP, Obenchain RL - BMC Psychiatry (2007)

Option characteristic curves and expected item total score for Item 1: Delusions. Option characteristic curves (solid lines) and expected item total score (dashed line) are plotted as a function of scores on the Positive Symptomatology Subscale form the PANNS, expressed as standard normal scores (lower x-axis) and expected total scores (upper x-axis). The probability of endorsing an option characteristic curve (solid lines) is scaled on the left y-axis and the expected item score (dashed line) is scaled on the right y-axis. Many features of an ideal item are evident in this plot.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211479&req=5

Figure 2: Option characteristic curves and expected item total score for Item 1: Delusions. Option characteristic curves (solid lines) and expected item total score (dashed line) are plotted as a function of scores on the Positive Symptomatology Subscale form the PANNS, expressed as standard normal scores (lower x-axis) and expected total scores (upper x-axis). The probability of endorsing an option characteristic curve (solid lines) is scaled on the left y-axis and the expected item score (dashed line) is scaled on the right y-axis. Many features of an ideal item are evident in this plot.
Mentions: Item 1, from the PANSS Positive Factor subscale, assesses suspiciousness, defined as "Beliefs which are unfounded, unrealistic, and idiosyncratic." Option characteristic curves for this item are presented in the second panel of Figure 2 and show that the probability of rating Option 1, assessing an "absence of symptoms," decreases rapidly as the severity of positive psychotic symptoms begins to increase. Meanwhile, the probability of endorsing the more severe levels of Delusions begins to increase rapidly with increases in the severity of positive symptoms.

Bottom Line: Statistical 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Psychology, University of Ottawa, Ottawa, Canada, and The Provincial Centre of Excellence for Child and Youth Mental Health, Ottawa, Ontario, Canada. dsantor@uottawa.ca

ABSTRACT

Background: Statistical 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.

Methods: Option 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.

Results: Our 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.

Conclusion: This 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.

Show MeSH
Related in: MedlinePlus