Abstract
BackgroundThe PANSS (Positive and Negative Syndrome Scale) is one of the most important rating instruments for patients with schizophrenia. Nevertheless, there is a long and ongoing debate in the psychiatric community regarding its mathematical properties.All 30 items range from 1 to 7 leading to a minimum total score of 30, implying that the PANSS is an interval scale. For such interval scales straightforward calculation of relative changes is not appropriate. To calculate outcome criteria based on a percent change as, e.g., the widely accepted response criterion, the scale has to be transformed into a ratio scale beforehand. Recent publications have already pointed out the pitfall that ignoring the scale level (interval vs. ratio scale) leads to a set of mathematical problems, potentially resulting in erroneous results concerning the efficacy of the treatment.MethodsA Pubmed search based on the PRISMA statement of the highest-ranked psychiatric journals (search terms "PANSS" and "response") was carried out. All articles containing percent changes were included and methods of percent change calculation were analysed.ResultsThis systematic literature research shows that the majority of authors (62%) actually appear to use incorrect calculations. In most instances the method of calculation was not described in the manuscript.ConclusionsThese alarming results underline the need for standardized procedures for PANSS calculations.
Highlights
The PANSS (Positive and Negative Syndrome Scale) is one of the most important rating instruments for patients with schizophrenia
As pointed out in a previous paper [2], the PANSS is a 30 item interval scale ranging from 1-7 which implies that computations of ratios are not appropriate
Journals focusing on topics not related to the PANSS and schizophrenia, such as Molecular Psychiatry or journals specialising in adolescent psychiatry, were excluded
Summary
The PANSS (Positive and Negative Syndrome Scale) is one of the most important rating instruments for patients with schizophrenia. Recent publications have already pointed out the pitfall that ignoring the scale level (interval vs ratio scale) leads to a set of mathematical problems, potentially resulting in erroneous results concerning the efficacy of the treatment. As pointed out in a previous paper [2], the PANSS is a 30 item interval scale ranging from 1-7 which implies that computations of ratios (e.g. percent changes, like calculation of XX% PANSS reduction from baseline to final endpoint) are not appropriate. Ignoring this fact leads to severe mathematical problems, resulting in an underestimation of the actual response rate and potentially even to erroneous results. In a comment on this article [3], Leucht et al have cited such erroneous calculation methods as one reason for low response rates in studies on second generation antipsychotic drugs
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