PRELIMINARY VALIDATION OF THE NORTH-EAST VISUAL HALLUCINATION SCALE SEVERITY SCORE IN LEWY BODY DISEASES

Abstract

Background Visual hallucinations (VH) are a common symptom of Parkinson's disease (PD), Parkinson’s disease dementia (PDD) and dementia with Lewy bodies (DLB) and other disorders. Several self-rated interviews (Queen Square Visual Hallucination Inventory, William et al. 2008; North East Visual Hallucinations Interview NEVHI, Mosimann et al. 2008; Tottori University Hallucinations Rating Scale TUHARS, Wada-Isoe et al. 2008; Rush Hallucination Inventory, Goetz et al. 2011) and informant-rated questionnaires (Neuropsychiatric Inventory NPI, Cummings et al.1994; Informant NEVHI) have been developed to assess the characteristics of VH. However, there is no validated measure of VH severity which would be usable in treatment trials. The aim of this study was to develop a new severity score for the NEVHI and to evaluate its reliability and convergent and discriminant validity. Methods Severity scores were designed for individual aspects of VH phenomenology (Complex, Illusions, Simple, Passage/Shadow, Presence). Sixty-four individuals recruited from three participant populations: PDD with VH (n = 32), PDD without VH (n = 11), and healthy age matched controls (n = 21) completed the NEVHI along with evaluations of cognitive (mini mental state exam MMSE, Folstein et al. 1975; Cambridge cognitive test battery CAMCOG, Roth et al.1986) and visual (pareidolia task, Uchiyama et al. 2012)functioning as part of the VEEGSTIM study based in Newcastle University, UK. The hallucination items from the informant-rated NPI were used to assess the convergent and discriminant validity of the NEVHI Severity scores. Results The NEVHI identified VH in 96.9% (n=31) PDD with VH group using the patient (self-rated) NEVHI, of which 40.6% were simple VH, 84.4% Complex VH, 48.4% Illusions, 64.5% Presence, 46.9% Shadow. The NEVHI Complex Severity score strongly correlated with the NPI hallucination severity (rho=0.642, p<0.001) and NPI total score (rho=0.642, p<0.001). Significant correlations were also observed between the NEVHI Complex Severity score and measures of pareidolia frequency (rho= - 0.522, p=0.003). Conclusions The preliminary results demonstrate good convergent validity between the NEVHI complex Severity score and informant-reported NPI. A validated severity score will be a valuable tool for baseline and post-intervention testing in research and drug trials.