Update on the psychometric properties for the Italian version of the Aachen Aphasia Test (IT-AAT)

Abstract

ABSTRACT Background The Aachen Aphasia Test (AAT) is still the main test in use for the evaluation of aphasic deficits in German-speaking individuals (Huber et al., 1983, 1984). The test has also been adapted to the Italian language (Luzzatti et al., 1996) and was administered to 384 people with aphasia (PWA) almost exclusively after left-hemisphere brain damage (plus 24 individuals with residual symptoms and 8 without aphasia) and 88 control individuals. The study of construct validity and reliability, as well as norm data, were based on those 343 PWA who passed the preliminary examination for applicability of the Token Test. Aims Motivated by current calls for improving the quality of outcome measures in aphasiology, we re-analyzed the psychometric properties of the Italian version of the AAT (IT-AAT) in an enlarged participant sample, and, for key analyses, with more recent psychometric methods. The overall sample comprised 674 PWA (plus 89 individuals with left-brain damage, including 60 individuals with residual aphasic symptoms and 29 individuals without aphasia). The investigation of construct validity, reliability, and extended norm data was based on the subset of 598 PWA who passed the AAT Token Test inclusion criterion. Main Contributions Assessment of construct validity, differential validity, and reliability aspects corroborated the earlier test properties. The extended norm data applied to the performance of an exemplary PWA yielded unanimous assignment to a Wernicke-type aphasia at initial assessment, which evolved, after speech-language therapy, to an impairment pattern consistent with conduction aphasia, characterized by disproportionately poorer performance in subtest Repetition than in subtest Comprehension. Significant improvement could be demonstrated for all subtests, which remained reliable even after taking into account the average expected increase in scores due to spontaneous recovery. Conclusions The psychometric properties and the enlarged normative sample size are well suited for a valid application of diagnostic psychometric single-case analysis procedures to individual patients’ AAT performance profiles and their comparison to detect changes in performance over time.