Informant- and Self-Appraisals on the Psychosis and Hallucinations Questionnaire (PsycH-Q) Enhances Detection of Visual Hallucinations in Parkinson's Disease.

Background: Clinicians vary in their ability to elicit and interpret hallucinatory symptoms in patients with Parkinson's disease (PD). There is limited evidence for informant-report measures of PD hallucinations as adjuncts to clinician-rated scales.

Objectives: To determine the utility of an informant version of the validated Psychosis and Hallucinations Questionnaire (PsycH-Q) for assessing the presence and severity of hallucinations in PD; and, to evaluate accuracy of clinician judgements by comparison with informant report and self-report.

Methods: One hundred sixty-three PD patient-informant dyads completed self- and informant-report versions of PsycH-Q and three common questionnaire measures: Neuropsychiatric Inventory Questionnaire; Parkinson's Psychosis Questionnaire; and Scales for Outcomes in Parkinson's disease-Psychiatric Complications. We compared self-ratings and informant ratings across analogous subscales for the presence of hallucinations with clinician interview ratings on MDS-UPDRS as a diagnostic standard.

Results: There was a low level of agreement between dyads (average κ = 0.39; κ range = 0.32-0.47;  < 0.001), and patients indicated the highest prevalence of hallucinations compared to informant or clinician estimates. Clinician interview missed 32% of PsycH-Q hallucinators identified by dyads. Relative to the sample, 22 patients with exclusively clinician-appraised hallucinations had poorer overall quality of life measured by the Parkinson's Disease Questionnaire.

Conclusions: The sole use of clinician-rated scales may underestimate prevalence of PD hallucinations, and there is room for introducing self- and informant-report tools. Nonetheless, clinician appraisals are critical in cases when informant and patient insight might be affected by the impact of illness on quality of life.