Classifying aphasias: Cluster analysis of western aphasia battery and boston diagnostic aphasia examination results

Abstract The Western Aphasia Battery (WAB) and the Boston Diagnostic Aphasia Examination (BDAE) are designed to classify the aphasias. Previous reports indicate that patients classified as demonstrating one type of aphasia on one test may be classified as having a different type of aphasia on the other test. We investigated this discrepancy by analysing the same patients' performance on each test with a statistical clustering procedure. Results indicated that cluster profiles showed poor agreement with the original classification on both tests. Only 30% of the patients' original classification on the WAB and 38% of patients' original classification on the BDAE corresponded with the classifications obtained in the cluster analysis. The BDAE system for classification resulted in more homogeneous clusters than the WAB system for classification. These results are discussed in reference to differences between the classification systems used by the respective aphasia examinations.