How object naming dissociates from repetition and comprehension impairments when post stroke aphasia is less severe

Object naming is widely used for assessing aphasia. We provide the first quantitative analysis of how well: (A) impaired spoken object naming (anomia) detects auditory repetition and/or speech comprehension impairments and (B) intact naming rules these impairments out. Participants were 382 stroke survivors (1 month to 34 years post-stroke) with impaired naming, repetition and/or comprehension, but intact object recognition. We assessed: (1) Incidence of anomia within the full sample; (2) its positive predictive value (PPV), i.e., the proportion of patients with anomia who had impaired repetition and/or comprehension; (3) its sensitivity to other impairments, i.e., the proportion of patients with impaired repetition or comprehension who had anomia; and (4) how object naming, word repetition, sentence repetition, word comprehension and sentence comprehension compared in their incidence, PPV and sensitivity, when each was treated as the reference task. Incidence, PPV and Sensitivity of anomia were 66%, 90% and 63% across sample; 93%, 100% and 93% for the most severely aphasic patients and 50%, 86% and 46% for the remaining patients. These metrics were not higher for object naming than sentence comprehension, sentence repetition and word repetition; but word comprehension showed markedly lower incidence and sensitivity. Although anomia may be the most salient symptom of aphasia in everyday conversation, our findings (i) challenge assumptions that object naming is a superior test of aphasia, (ii) show that the presence of anomia was insensitive to 37% of patients with repetition and comprehension impairments and (iii) highlight how PPV and sensitivity within an aphasic sample are influenced by impairment severity, task dependency, measurement variability and inter-patient differences.