On the use of the Positive and Negative Syndrome Scale in randomized clinical trials

Introduction: In the last 25 years, the Positive and Negative Syndrome Scale (PANSS) has been largely used to assess schizophrenia symptom intensity, but little information is available on how this scale was generally applied when evaluating the efficacy of new therapies in randomized clinical trials. Aims: The study focused on (i) how PANSS results are depicted within research articles; (ii) the PANSS-subscale structures mostly used in randomized clinical trials; (iii) the demographic and symptomatic characteristics of individuals enrolled in these clinical studies. Methods: A systematic PubMed Search was carried out using the keywords "PANSS" and "Randomized Clinical Trials". Results: The analysis of retrieved articles confirmed that PANSS constitutes a valuable psychometric instrument to investigate the effects induced by pharmacological and non-pharmacological therapies in schizophrenia individuals. However, the information potentially provided by this scale was only partially reported in research articles, when characterizing the symptomatic features of patients at baseline. Furthermore, the rationale behind the use of a specific PANSS-subscale structure was rarely mentioned in PANSS-RT articles, and the choice appeared to be mostly related to the trial sample size or geographic/cultural factors. Unexpectedly, it was estimated that 95% of schizophrenic individuals enrolled in randomized clinical trials showed a symptom intensity ranging from "minimal" to "moderate" both in PANSS total and PANSS subscales. Conclusions: A further effort is needed to increase the amount of qualitative and quantitative information potentially provided by PANSS within research articles, since a more complete description of the symptomatic characteristics of patients enrolled in randomized clinical trials may improve the transferability of the results to the clinical practice and drug development research. Possibly, the completeness of PANSS-subscale scores and a larger use of factorial analyses may provide useful data for reaching a consensus on which PANSS-subscale structure better represents the symptomatic profiles of schizophrenic individuals. The possibility that the structured PANSS interview may limit the enrollment of schizophrenic individuals with "severe" symptoms should be carefully analyzed, so to avoid a possible gap between the results of clinical trials and the everyday clinical practice.