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

Structural validity of the 5-item World Health Organization Well-being Index (WHO-5) in patients with schizophrenia spectrum disorders

BACKGROUND

When monitoring the severity and impact of schizophrenia spectrum disorders, a measure of subjective well-being should ideally accompany measures of symptom severity and medication side effects. The self-reported 5-item World Health Organization Well-being Index (WHO-5) is a brief, generic, and widely used measure of subjective well-being. However, the structural validity of the WHO-5, namely, whether the individual item scores can be combined to produce a meaningful total score, has not been examined among patients with schizophrenia spectrum disorders.

METHOD

Utilizing data from 399 Danish patients with schizophrenia spectrum disorders attending the Psychiatric Services of the Central Denmark Region, we employed Rasch analysis to examine the structural validity (i.e., unidimensionality, overall fit to the Rasch model, and differential item functioning) of the WHO-5.

RESULTS

The WHO-5 was found to be unidimensional with no differential item functioning for age, sex, or inpatient/outpatient status. However, in the initial analysis, some misfit to the Rasch model, partially caused by the disordering of response categories, was evident. In adjusted analyses in which the item response categories 2 (Less than half of the time) and 3 (More than half of the time) were merged, overall fit to the model was improved.

CONCLUSIONS

When two item response categories were merged, the Danish version of the WHO-5 was found to be structurally valid for patients with schizophrenia spectrum disorders. This suggests that the WHO-5 holds promise as a measure of subjective well-being in this patient population.

Are informants required to obtain valid ratings on the Positive and Negative Syndrome Scale (PANSS)?

Ratings on the Positive and Negative Syndrome Scale (PANSS) are ideally based on both a patient interview and an informant questionnaire. In research and clinical settings, however, the informant questionnaire is often omitted. This study investigated the consequences of omitting informant information by comparing PANSS ratings of patients with schizophrenia (n = 49 patients, 77 ratings) conducted with and without informant information, respectively. Additionally, changes in symptom severity over time based on ratings with and without informant information were also compared for the full PANSS and the six-item version of the PANSS (PANSS-6). PANSS ratings including informant information were higher than those without, both at the total score and individual item level. Additionally, the full PANSS appeared less "responsive" to baseline-to-endpoint changes for ratings without informant information compared to ratings including informant information, while no differences were found for the PANSS-6.

Initial severity of the Positive and Negative Syndrome Scale (PANSS)-30, its main subscales plus the PANSS-6, and the relationship to subsequent improvement and trial dropout: a pooled participant-level analysis of 18 placebo-controlled risperidone and paliperidone trials

Greater initial severity on the 30-item Positive and Negative Syndrome Scale (PANSS-30) correlates positively with antipsychotic-placebo separation and trial dropout, but it is unknown whether these associations are present also on PANSS-derived subscales. We assessed the relationship between initial severity and antipsychotic-placebo separation as measured by PANSS-30 and four PANSS symptom subscales: the positive (PANSS-POS), negative (PANSS-NEG), general (PANSS-GEN) and 6-item (PANSS-6) subscales, using patient-level data from 18 placebo-controlled risperidone and paliperidone trials. Analysis of covariance in the intention-to-treat population (last-observation-carried-forward) was used to assess antipsychotic-placebo separation and trial dropout. Across 6685 participants (90% schizophrenia, 10% schizoaffective disorder), the initial severity-by-treatment interaction was statistically significant for PANSS-30 (beta: -0.155; p < 0.001) and all PANSS subscales (beta range: -0.097 to -0.135; p-value range: < 0.001 to 0.002). In all cases, antipsychotic-placebo differences increased with initial severity. Judging by the distribution of relative outcomes (percent remaining symptoms), the interaction was partly explained by an increased chance of responding, but also by larger numerical responses in those who did respond, as initial severity increased. Except for PANSS-NEG, high initial severity on all PANSS scales predicted increased trial dropout, although not statistically significantly so for PANSS-6. In summary, we thus replicate previous findings showing greater initial severity to predict larger antipsychotic-placebo separation and extend these results to four PANSS subscales. For PANSS-POS and PANSS-GEN, but not for PANSS-NEG and PANSS-6, we also replicate the association between initial severity and trial dropout. Patients with low initial negative symptom severity were identified as a group of particular interest for further study since their results diverged most from the average both with regard to antipsychotic-placebo separation (low separation measured by PANSS-NEG) and trial dropout (high level).