Validation of the Psychosis and Hallucinations Questionnaire in Non‐demented Patients with Parkinson's Disease

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Abstract
People diagnosed with Parkinson's disease (PD) frequently experience visual and non‐visual hallucinations often with comorbid psychosis, however, there is currently no gold standard tool for accurately assessing these symptoms. To address this problem, we designed a novel questionnaire to evaluate the presence of hallucinatory and psychotic symptoms in PD, as well as related symptoms, such as attentional dysfunction and sleep disturbance. We administered the 20‐item Psychosis and Hallucinations Questionnaire (PsycH‐Q) and three common questionnaire measures in a large cohort of 197 patients with idiopathic PD via a postal survey. We established concurrent validity, convergent validity, and internal consistency of the questionnaire and then assessed test‐retest reliability in a subcohort of 44 patients. PsycH‐Q was found to be a valid instrument when analogous items were compared across three other existing tools (Spearman's rho range: 0.34–0.64; P < 0.01). PsycH‐Q demonstrated a strong relationship between self‐reported hallucinations and psychosis and symptoms of the broader hallucinatory phenotype (Kendall's tau = 0.41; P  <   0.01; positive predictive value = 0.97). PsycH‐Q also displayed a high level of internal consistency (Cronbach's alpha = 0.900; range, 0.696–0.923) and reproducibility (intraclass correlation coefficient = 0.928). PsycH‐Q is a simple, valid, self‐completed instrument that reliably identifies hallucinations and psychosis in PD and has the ability to characterize related patterns of attentional and sleep impairments. As such, PsycH‐Q is a highly valuable tool for use in both clinical and research settings.
Funding Information
  • Parkinson's NSW Seed Grant
  • Australian Rotary Health
  • Australian Government
  • National Health & Medical Research Council of Australia (630434, 1008117, 1003007)

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