The Pareidolia Test: A Simple Neuropsychological Test Measuring Visual Hallucination-Like Illusions

BACKGROUND: Visual hallucinations are a core clinical feature of dementia with Lewy bodies (DLB), and this symptom is important in the differential diagnosis and prediction of treatment response. The pareidolia test is a tool that evokes visual hallucination-like illusions, and these illusions may be a surrogate marker of visual hallucinations in DLB. We created a simplified version of the pareidolia test and examined its validity and reliability to establish the clinical utility of this test. METHODS: The pareidolia test was administered to 52 patients with DLB, 52 patients with Alzheimer’s disease (AD) and 20 healthy controls (HCs). We assessed the test-retest/inter-rater reliability using the intra-class correlation coefficient (ICC) and the concurrent validity using the Neuropsychiatric Inventory (NPI) hallucinations score as a reference. A receiver operating characteristic (ROC) analysis was used to evaluate the sensitivity and specificity of the pareidolia test to differentiate DLB from AD and HCs. RESULTS: The pareidolia test required approximately 15 minutes to administer, exhibited good test-retest/inter-rater reliability (ICC of 0.82), and moderately correlated with the NPI hallucinations score (r(s) = 0.42). Using an optimal cut-off score set according to the ROC analysis, and the pareidolia test differentiated DLB from AD with a sensitivity of 81% and a specificity of 92%. CONCLUSIONS: Our study suggests that the simplified version of the pareidolia test is a valid and reliable surrogate marker of visual hallucinations in DLB.