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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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Option characteristic curves and expected item total score for Item 5: Grandiosity. 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). Option characteristic curves (solid lines) indicate that a number of opportunities for improvement. Options 2, 3 and 4 overlap substantially as do Options 6 and 7 suggesting rating these options is inherently difficult for raters. Option 1 in this item was most frequently endorsed by over half the sample, indicating that these options are only endorsed as a higher level of symptoms severity than in other options. The item characteristic curve (broken line) increases smoothly in all but the lowest region of symptom severity, but increases more slowly than the item characteristic curve in Item 1 or 3. Expected item scores for this item are generally lower at comparable regions of symptom severity than for Items 1 or 3.
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Figure 4: Option characteristic curves and expected item total score for Item 5: Grandiosity. 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). Option characteristic curves (solid lines) indicate that a number of opportunities for improvement. Options 2, 3 and 4 overlap substantially as do Options 6 and 7 suggesting rating these options is inherently difficult for raters. Option 1 in this item was most frequently endorsed by over half the sample, indicating that these options are only endorsed as a higher level of symptoms severity than in other options. The item characteristic curve (broken line) increases smoothly in all but the lowest region of symptom severity, but increases more slowly than the item characteristic curve in Item 1 or 3. Expected item scores for this item are generally lower at comparable regions of symptom severity than for Items 1 or 3.

Mentions: Grandiosity, Item 5, is defined as "Exaggerated self-opinion and unrealistic convictions of superiority, including delusions of extraordinary abilities, wealth, knowledge, fame, power, and moral righteousness" [1]. Figure 4 depicts the option characteristic curves for this item as being generally flatter and less peaked than those of other items. Indeed, the probability of endorsing Options 2, 3, and 5 from Item 5 increase much slower than the corresponding options for Items 1 or 3.


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 5: Grandiosity. 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). Option characteristic curves (solid lines) indicate that a number of opportunities for improvement. Options 2, 3 and 4 overlap substantially as do Options 6 and 7 suggesting rating these options is inherently difficult for raters. Option 1 in this item was most frequently endorsed by over half the sample, indicating that these options are only endorsed as a higher level of symptoms severity than in other options. The item characteristic curve (broken line) increases smoothly in all but the lowest region of symptom severity, but increases more slowly than the item characteristic curve in Item 1 or 3. Expected item scores for this item are generally lower at comparable regions of symptom severity than for Items 1 or 3.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Option characteristic curves and expected item total score for Item 5: Grandiosity. 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). Option characteristic curves (solid lines) indicate that a number of opportunities for improvement. Options 2, 3 and 4 overlap substantially as do Options 6 and 7 suggesting rating these options is inherently difficult for raters. Option 1 in this item was most frequently endorsed by over half the sample, indicating that these options are only endorsed as a higher level of symptoms severity than in other options. The item characteristic curve (broken line) increases smoothly in all but the lowest region of symptom severity, but increases more slowly than the item characteristic curve in Item 1 or 3. Expected item scores for this item are generally lower at comparable regions of symptom severity than for Items 1 or 3.
Mentions: Grandiosity, Item 5, is defined as "Exaggerated self-opinion and unrealistic convictions of superiority, including delusions of extraordinary abilities, wealth, knowledge, fame, power, and moral righteousness" [1]. Figure 4 depicts the option characteristic curves for this item as being generally flatter and less peaked than those of other items. Indeed, the probability of endorsing Options 2, 3, and 5 from Item 5 increase much slower than the corresponding options for Items 1 or 3.

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