A novel scale to assess psychosis in patients with parkinson's disease.

BACKGROUND: Organic psychosis effects up to 70 % of patients with PD at some point yet no widely accepted scale for this entity exists.

METHODS: We developed a 10 question PD specific psychosis severity scale that we feel has good content validity. It asks about the presence, severity, frequency, and consequences of the hallucinations (visual, auditory, olfactory) and delusions.

RESULTS: Fifty different PD patients with psychosis and 25 PD patients without psychosis were included, and serial information was available in 21 of those encounters with psychosis. In psychosis subjects, results were normally distributed: mean 17.23 (SD = 6.30). In those without psychosis 14 % scored >0, mean 0.36 [range0-7]. The intra-rater, inter-class correlation coefficient was excellent (N = 21 pairs of observations seven days apart, ICC = 0.87). Inter-rater reliability (two different raters, N = 46 pairs) was outstanding for the entire group, ICC = 0.92). As expected visual hallucinations were most common (mean = 3.13). The presence of delusions was associated with greater total scores.

CONCLUSIONS: This scale, specifically designed for PD psychosis is easy to administer and has impressive metrics.