Object decision test (BORB): normative data for the adult Quebec population and performance in Alzheimer's disease and the semantic variant of primary progressive aphasia

Object decision (OD) test is one subtest of the Birmingham Object Recognition Battery (BORB). It is useful for differential diagnosis among several neurodegenerative diseases. However, normative data provided with this battery count on very few subjects and do not control for the effect of age, which limits interpretability. The purpose of Study 1 was to provide normative data for the OD test of the BORB (version Ahard). The objectives of Study 2 were to establish the diagnostic validity of this task and predictive validity of the normative data in the case of the semantic variant of primary progressive aphasia (svPPA) and Alzheimer's disease (AD).Based on multiple linear regressions, equations to calculate Z-scores corrected for age were provided for 130 participants aged from 47 to 89years. Performance of 20 healthy participants was compared to that of 14 individuals with svPPA and 18 with AD. After controlling for confounders, participants with svPPA had a lower total score than controls and AD participants. AD participants had a poorer performance than controls only when chimeric objects were considered. Among those with a deficit on the total score of the test, 94% (17/18, including 12 with svPPA) were correctly identified as having a pathological condition (svPPA or AD). This test could help refine differential diagnosis between svPPA and AD patients, especially before the deficits of episodic memory show up.