Validation of a Psycho-Sensory hAllucinations Scale (PSAS) in schizophrenia and Parkinson's disease

If hallucinations are the most common of schizophrenic symptoms, they have been described in other pathologies such as Parkinson's disease (PD) but may differ considerably in their phenomenology. However, no multi-modal clinical scale with a transnosographic approach has been developed today. The purpose of this study was to create and validate a new tool for the hetero-assessment of all sensory modalities of hallucinations schizophrenia (SCZ) and in PD.

Scale items were generated by literature review and validated by medical board. A study was then made to evaluate psychometric properties of the Psycho-Sensory hAllucinations Scale (PSAS) that include four domains (auditory, visual, olfactory and gustatory, cenesthetic modalities) and one specific item 'guardian angel'.

It was then validated in 137 patients: 86 PD (53.5% male; mean age=53.3years) and 51 SCZ (64.7% male; mean age=38.5years). Factorial analysis of the PSAS found four factors. The PSAS showed good internal consistency [Kuder-Richardson alpha coefficient 0.49 to 0.77] and good test-retest reliability [Agreement %=0.75 to 0.97] and inter-rater reliability [Agreement %=0.78 to 1.0]. The convergent validity illustrates the concomitant evaluation of the concept between PSAS and PANSS P3 and UPDRS1 I2.

The PSAS can be useful to describe the whole hallucination and its evolution during the course of the disease and treatment in schizophrenia and PD. Moreover, it can allow us to undertake a clinic-pathological comparison of hallucination modalities between these two diseases, to enhance our understanding of their precise neurological mechanisms.