Innovations In Clinical Neuroscience

NOV-DEC 2017

A peer-reviewed, evidence-based journal for clinicians in the field of neuroscience

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74 ICNS INNOVATIONS IN CLINICAL NEUROSCIENCE November-December 2017 • Volume 14 • Number 11–12 R E V I E W fewer factors) could be more robust than models using all 30 items. Further, a shorter PANSS version also offers the possibility to retain only those PANSS items that are psychometrically very robust. We have shown using item response analysis (IRT) that not all PANSS items demonstrate optimal option characteristic curves (OCCs) and item characteristic curves (ICCs), while most items performed very well. 15, 16 A shorter PANSS could potentially allow for retainment of the items that perform well psychometrically. Finally, Bech 17 has pointed out that in order to obtain valid measures of illness severity, it is essential that rating scales are both scalable and transferable. By "scalability," Bech means that each item in a rating scale "provides unique information regarding syndrome severity and is a statistical prerequisite for using the total score as a measure of overall severity." Further, a "severity rating scale has to have an additive structure, implying that each manifest item scores in the scale can be added to a simple sum, which is a psychometrically valid measure of overall illness severity." 17 Ostergaard et al 18 found that neither the full PANSS-30 nor any other, shorter versions of the PANSS have been evaluated for their scalability by means of the Rasch rating scale model. These authors proposed a six-item PANSS, whereby each item was chosen based on its scalability, meaning that all items provide unique information regarding syndrome severity. Disadvantages of a shorter PANSS. Whatever the scientific and practical rationale is for the development of a shorter version of the PANSS, there are a number of potential disadvantages to be kept in mind. One of the most important is the issue of successful comparability and translation of results between studies using the full PANSS and those studies using a shorter version. While there might be statistical models capable of translating PANSS total scores from a short version to the full version, 16 this will always introduce a complicating factor in comparing results between studies. Notably, this issue was fairly easy to mitigate when the results obtained with PANSS ratings had to be compared with results measured with BPRS ratings, given that the PANSS contains all BPRS items. Another issue potential problem is that the a priori chosen focus in a short PANSS version, given the restricted number of items, might include predominantly treatment-responsive items. This would help to discriminate between active treatments and placebos in controlled clinical trials. However, this would, at the same time, limit explorations of newer treatments of interventions that are not dopamine blockers, the main model of all antipsychotic pharmacological treatments until now. Another potential limitation related to this issue is that a short PANSS might focus on a single psychopathological domain and not measure other common schizophrenia domains. On the research side, a brief PANSS version with significantly fewer items could potentially present psychometric challenges in terms of construct validity, discriminant validity, and sensitivity to change to statistically evaluate significant changes to a treatment intervention. Short scales extracted from a longer scale can compromise the reliability of an instrument. 7 As items of the scale are removed, the Cronbach's alpha tends to decrease. Scales with many items tend to be more reliable, with higher alpha values. 8 Finally, a short version of the PANSS might have to be phase- specific and not be applicable to all illness phases over time. With these multiple issues in mind, this article presents a comprehensive overview of existing brief PANSS measures, including their strengths and limitations, and discusses some possible next steps in more detail. BRIEF PANSS MEASURES The Mini-PANSS. Using the new statistical technique of item response analysis on all 30 PANSS items, Santor et al 15 found that most items forming the positive and negative subscales of the PANSS performed very well, but several areas for improvement in items of the general psychopathology subscale were identified. The positive and the negative subscales were more discriminating of individual differences in symptom severity than the general psychopathology subscale score and were shown to be more efficient on average than the 30-item total score. These authors suggested that the retained 14 items could form a shorter version of the PANSS— the 14-item PANSS. Building further on these data and using the same IRT technique, Kahn et al 16 examined baseline PANSS scores from 7,187 patients with schizophrenia or schizoaffective disorder who were enrolled in psychopharmacology trials in the years 1995 to 2005. 16 OCCs and ICCs were constructed to examine the probability of rating each of seven options (equaling levels of severity) within each of the 30 PANSS items as a function of subscale severity, and summed-score linking was applied to items selected for the Mini-PANSS. This statistical process resulted in six of the seven positive symptom items, six of the seven negative symptom items, and seven of the 16 general psychopathology items, all of which were retained as items that performed well and as closely linked to overall severity. The authors retained these 19 items for inclusion in the Mini-PANSS. They also produced, via using summed score-linking and linear interpolation, a translation table for comparing total subscale scores of the Mini-PANSS with total subscale scores of the original PANSS. 16 Results showed scores on the subscales of the Mini-PANSS could be linked with scores on the original PANSS subscales, with very little bias. The authors also examined similarities and differences between the 30-item PANSS and the Mini-PANSS using a series of descriptive analyses, including high correlations between subscale and total scores. Results of the principal component analysis of the Mini-PANSS assumed dimensionality for all three of the subscales. The elimination of the under-performing PANSS items resulted in high correlation between PANSS 30-item subscales and Mini-PANSS subscales, indicating that omission of these items in future clinical trials is not likely to significantly alter the PANSS subscales. Such a 19-item Mini-PANSS might be more reliable given the psychometric soundness of the retained items, might require shorter administration and training time, and might possibly reduce the sample size needed for future research studies. However, the 19-item Mini-PANSS still needs to be tested for its construct validity, reliability, and sensitivity to change. Specificity and cutoff scores for the Mini-PANSS also need to be determined for improvement and remission. Another consideration to investigate is the Mini-PANSS's ability to better separate placebo response from antipsychotic response. The Brief PANSS. Yamamoto et al 19

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