Validation of ratings on the six-item Positive and Negative Syndrome Scale obtained via the Simplified Negative and Positive Symptoms Interview among outpatients with schizophrenia
Cecilie Marie Nielsen, Pernille Kølbæk, David E. Dines, Martin Locht Pedersen, Andreas Aalkjær Danielsen, Camilla Holmgård, Sanne Wissing, Anne-Mette Esbøl, Nina Friis Bak Fuglsang, Tuan D. Nguyen, Ole Mors, Mark Opler, Christoph U. Correll, Søren Dinesen Østergaard
Abstract
Background: The six-item Positive and Negative Syndrome Scale (PANSS-6) is a measure of the severity of core symptoms of schizophrenia, which can be administered via the brief Simplified Negative and Positive Symptoms Interview (SNAPSI). A recent study has confirmed the validity of PANSS-6 ratings as derived by SNAPSI (PANSS-6 SNAPSI ) among inpatients with schizophrenia. Aims: We aimed to test the validity of PANSS-6 SNAPSI among outpatients with schizophrenia using PANSS-6 ratings extracted from the 30-item PANSS-30 as derived by the Structured Clinical Interview for the Positive and Negative Syndrome Scale (PANSS-6 SCI-PANSS ) as a gold standard reference. Methods: PANSS-6 SNAPSI and PANSS-6 SCI-PANSS ratings were obtained at two time points by independent raters with established inter-rater reliability. Agreement between PANSS-6 SNAPSI and PANSS-6 SCI-PANSS ratings was estimated via intra-class coefficients (ICCs) and responsiveness over time was quantified using Spearman’s rank correlation coefficients. Post hoc “leave-one-out” analyses were carried out, in which each rater in turn was excluded from the ICC calculations. Results: Seventy-three outpatients with schizophrenia participated in the study (mean age: 38.3 years; 56% males). The ICC for PANSS-6 SNAPSI versus PANSS-6 SCI-PANSS was 0.67 [95%CI = 0.56–0.76] and the Spearman’s rank correlation coefficient for responsiveness was 0.40 ( p = 0.004). When data from a specific outlying rater were excluded, the ICC for PANSS-6 SNAPSI versus PANSS-6 SCI-PANSS was 0.75 [95% CI = 0.63–0.83] and the Spearman’s rank correlation coefficient for responsiveness was 0.55 ( p = 0.018). Conclusions: We found PANSS-6 SNAPSI ratings to have acceptable clinical validity, suggesting that PANSS-6 SNAPSI can be used for both inpatients and outpatients with schizophrenia.