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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 for Item 19: Mannerisms and posturing. Option characteristic curves describing the probability with ratings of 3 or less are made as a function of symptom severity for items recommended to define symptom remission in patients. Results show that the option characteristic curves for this item will be endorsed at a much more severe level of symptomatology than other items and is therefore redundant or should be revised. The broken line (---) shows the option characteristic curves for a revised Item 19, where remission is defined on the basis of a score less than or equal to 2 (rather than 3).
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Figure 7: Option characteristic curves for Item 19: Mannerisms and posturing. Option characteristic curves describing the probability with ratings of 3 or less are made as a function of symptom severity for items recommended to define symptom remission in patients. Results show that the option characteristic curves for this item will be endorsed at a much more severe level of symptomatology than other items and is therefore redundant or should be revised. The broken line (---) shows the option characteristic curves for a revised Item 19, where remission is defined on the basis of a score less than or equal to 2 (rather than 3).

Mentions: Andreasen and her colleagues [17] recently recommended that "symptom remission" be defined as achieving scores of 3 or less on each of 8 core symptoms: Delusions, Unusual Thought Content, Hallucinatory Behavior, Conceptual Disorganization, Mannerisms and Posturing, Blunted Affect, Social Withdrawal, and Lack of Spontaneity. To examine the appropriateness of this common cut-point, we modeled the probability of being rated 3 or less for each of these 8 symptoms as a function of symptom severity. Specifically, the response characteristic curves for endorsing Option 1, 2, or 3 were computed by summing across individual option characteristic curves. Results show that the probability of obtaining a score of 3 or less does decrease for 7 of the 8 core symptoms. For the "easy" Item 19 (Mannerisms and Posturing), the probability of obtaining a score of 3 or less decreases more slowly over a slightly wider range of symptom severity. This means that a person with a severity score of +2 has a probability of 0.5 of scoring 3 or less on Item 19 (Mannerisms and Posturing). Meanwhile, the probability of scoring 3 or less on any other item drops to less than 0.2 at a severity score of +2 having declined from a probability of 0.5 achieved at a much lower severity score (Figure 7).


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 for Item 19: Mannerisms and posturing. Option characteristic curves describing the probability with ratings of 3 or less are made as a function of symptom severity for items recommended to define symptom remission in patients. Results show that the option characteristic curves for this item will be endorsed at a much more severe level of symptomatology than other items and is therefore redundant or should be revised. The broken line (---) shows the option characteristic curves for a revised Item 19, where remission is defined on the basis of a score less than or equal to 2 (rather than 3).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Option characteristic curves for Item 19: Mannerisms and posturing. Option characteristic curves describing the probability with ratings of 3 or less are made as a function of symptom severity for items recommended to define symptom remission in patients. Results show that the option characteristic curves for this item will be endorsed at a much more severe level of symptomatology than other items and is therefore redundant or should be revised. The broken line (---) shows the option characteristic curves for a revised Item 19, where remission is defined on the basis of a score less than or equal to 2 (rather than 3).
Mentions: Andreasen and her colleagues [17] recently recommended that "symptom remission" be defined as achieving scores of 3 or less on each of 8 core symptoms: Delusions, Unusual Thought Content, Hallucinatory Behavior, Conceptual Disorganization, Mannerisms and Posturing, Blunted Affect, Social Withdrawal, and Lack of Spontaneity. To examine the appropriateness of this common cut-point, we modeled the probability of being rated 3 or less for each of these 8 symptoms as a function of symptom severity. Specifically, the response characteristic curves for endorsing Option 1, 2, or 3 were computed by summing across individual option characteristic curves. Results show that the probability of obtaining a score of 3 or less does decrease for 7 of the 8 core symptoms. For the "easy" Item 19 (Mannerisms and Posturing), the probability of obtaining a score of 3 or less decreases more slowly over a slightly wider range of symptom severity. This means that a person with a severity score of +2 has a probability of 0.5 of scoring 3 or less on Item 19 (Mannerisms and Posturing). Meanwhile, the probability of scoring 3 or less on any other item drops to less than 0.2 at a severity score of +2 having declined from a probability of 0.5 achieved at a much lower severity score (Figure 7).

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