Bridging the Measurement Gap Between Research and Clinical Care in Schizophrenia: Positive and Negative Syndrome Scale-6 (PANSS-6) and Other Assessments Based on the Simplified Negative and Positive Symptoms Interview (SNAPSI)

Abstract

There is currently a "measurement gap" between research and clinical care in schizophrenia. The main reason behind this gap is that the most widely used rating scale in schizophrenia research, the 30-item Positive and Negative Syndrome Scale (PANSS), takes so long to administer that it is rarely used in clinical practice. This compromises the translation of research findings into clinical care and vice versa. The aim of this paper is to discuss how this measurement gap can be closed. Specifically, the main points of discussion are 1) the practical problems associated with using the full 30-item PANSS in clinical practice; 2) how the brief, six-item version of the Positive and Negative Syndrome Scale (PANSS-6) was derived empirically from the full 30-item PANSS and what the initial results obtained with PANSS-6 entail; and 3) how PANSS-6 ratings, guided by the newly developed, 15-25-minute, stand-alone Simplified Negative and Positive Symptoms Interview (SNAPSI), might help bridge the measurement gap between research and clinical care in schizophrenia. The full 30-item PANSS is often used in research studies, but is too time consuming to allow for routine clinical use. Recent studies suggest that the much briefer PANSS-6 is a psychometrically valid measure of core positive and negative symptoms of schizophrenia and that the scale is sensitive to symptom improvement following pharmacological treatment. SNAPSI is a brief interview that yields the information needed to rate PANSS-6 (and other brief rating scales). We believe that PANSS-6 ratings guided by SNAPSI will help bridge the measurement gap between research and clinical care in schizophrenia.

Keywords: Schizophrenia; measurement-based care; psychometrics; rating scale.

Conflict of interest statement

FUNDING:No funding was provided for this article. DISCLOSURES:The home institution of SD Østergaard (Aarhus University) holds one-third of the copyright for the Simplified Negative and Positive Symptoms Interview (SNAPSI). Dr. Correll has been a consultant and/or advisor to or has received honoraria from: Alkermes, Allergan, Bristol-Myers Squibb, Gerson Lehrman Group, IntraCellular Therapies, Janssen/J&J, LB Pharma, Lundbeck, Medavante, Medscape, Neurocrine, Otsuka, Pfizer, Sunovion, Takeda, and Teva. He has provided expert testimony for Bristol-Myers Squibb, Janssen, and Otsuka. He served on a Data Safety Monitoring Board for Lundbeck and Pfizer. He received grant support from Takeda. The home institution of Dr. Correll (The Feinstein Institute for Medical Research, Manhasset, New York, USA) holds one-third of the copyright for the SNAPSI. The home institution of Dr. Opler (MedAvante-ProPhase Inc.) holds one-third of the copyright for the SNAPSI. Dr. Opler also has received grant funding from US NIMH, the Brain and Behavior Foundation (formerly NARSAD), the Stanley Research Foundation, and the Qatar National Research Fund.

Figures

FIGURE 1A–B.

A) Illustration of a hypothetical six-item rating scale, which is scalable because the symptoms represented by the items appear in an orderly fashion as the severity of the syndrome increases, such that scoring on higher prevalence items (less severe items) precedes scoring on lower prevalence items (more severe items). Thus, when an outcome measure is scalable, each individual item adds unique information about the severity of the latent syndrome being rated and the individual item scores can therefore be added to a meaningful total score. B) Illustration of the scalability of the Positive and Negative Syndrome Scale-6 (PANSS-6) based on the Rasch locations at baseline—This figure and the figure text is reproduced from Østergaard et al. with permission from the publisher via RightsLink.

FIGURE 2.

Positive and Negative Syndrome Scale-6 (PANSS-6)’s sensitivity to change in the severity of illness during treatment. Change in PANSS-6 scores by treatment based on data from Zimbroff et al. Statistics: analyses of covariance of mean change from baseline including the baseline score as covariate. *p<0.05, **p<0.01, ***p<0.001. This figure and the figure text is reproduced from Østergaard et al. with permission from the publisher via RightsLink.

FIGURE 3.

Correlation between Positive and Negative Syndrome Scale-6 (PANSS-6) and full PANSS (PANSS-30) total scores in the Clinical Antipsychotic Trials for Intervention Effectiveness (CATIE) study. The correlation between PANSS-6 total scores and PANSS-30 total scores from the entire CATIE study (ratings=5,081) was performed by means of Spearman correlation analysis. For PANSS-6 and PANSS-30, we also assessed the correlation between the 1) relative change in total score (current total score – baseline score)/baseline score); 2) total score ratio to baseline (current total score/baseline score); and 3) log (ratio to baseline) (i.e. log(current total score/baseline total score), which corresponds to: log (current total score) - log (baseline total score). These three correlations were based on 3,929 ratings (i.e., 5,081 ratings minus the baseline ratings). This figure and the figure text is reproduced from Østergaard et al. (8) with permission from the publisher via RightsLink.

FIGURE 4.

Illustration of the similarity of the trajectories of Positive and Negative Syndrome Scale-6 (PANSS-6) and full PANSS (PANSS-30) scores during the Clinical Antipsychotic Trials for Intervention Effectiveness (CATIE) Phase I study, stratified by treatment. The figure shows estimated polynomials of order three describing trajectories of PANSS-30 and PANSS-6 scores with treatment (weeks from baseline) as measured by the log(ratio to baseline). The models included drug-specific coefficients—four parameters for each drug—and were adjusted for tardive dyskinesia (SET 2 and SET 3) and exacerbation (all four sets). The SETs refer to those used for pairwise drug-comparisons in the CATIE publication by Lieberman et al. The comparison between pairs of drugs was carried out by the four degrees of freedom likelihood ratio test of the null hypothesis that all two times four coefficients in the polynomials shown above were equal. The results showed that PANSS-6 and PANSS-30 identified the exact same statistically significant (Bonferroni-adjusted level = 0.005) differences in antipsychotic efficacy, namely that olanzapine was superior to risperidone (p-value PANSS-6 = 0.0003 and p-value PANSS-30 = 0.0003) and ziprasidone (p-value PANSS-6 = 0.0018 and p-value PANSS-30 = 0.0046). This figure and the figure text is reproduced from Østergaard et al. with permission from the publisher via RightsLink.