The original version of WAB was designed based on the BDAE, accompanying certain system continuity. Subsequently, various versions of WAB appeared in the study for population with linguistic deficit in different countries, languages and diseases[18–20]. The severity of initial aphasia is closely related to the prognosis, which has been confirmed long ago. In that case, why not directly correlate the severity stratification of linguistic deficit through WAB-AQ value? Considering the above situation, when solving the problem of severity classification of aphasia in clinic, we plan to conduct a secondary cluster analysis on those with WAB-AQ scores less than 93.8 based on the original score division of WAB, so as to further optimize the evaluation system of aphasia and facilitate the clinical application of aphasia evaluation.
In this study, we performed a division of linguistic deficit levels using cutoff scores. The benefit of using a cluster analysis to define impairment levels of the WAB-AQ assessment is that the cutoff points are derived using an objective quantitative method. In practical research, many scholars take WAB as an index to judge the type and severity of aphasia and evaluate the curative effect and outcome[22, 23]. However, up to now, we have not retrieved the relevant literature on the stratification of aphasia severity corresponding to WAB-AQ scores. The existing stratification of aphasia may be more based on the subjective impression of clinicians. As described in the BDAE, 0 indicates that the patient has no meaningful language or auditory comprehension ability and 5 indicates that there is almost no discernible language impairment. Although in the clinical application of nervous system diseases, the diagnosis of language defects needs to be combined with more clinical data, such as imaging, biochemistry and pathophysiology, we hope to provide some convenience for language rehabilitation practitioners and patients through our research results.
In terms of the characteristics of linguistic deficit within each cluster, from the severe to the mild linguistic deficit group, there was an increase in WAB-AQ scores. In the WAB-AQ subtests, the scores of spontaneous speech, repetition and naming increased with the decrease of the severity of aphasia, while there was no significant statistical difference in auditory comprehension between the mild and moderate groups. According to the scores of all subitems, we tried to describe the characteristics of the groups at three linguistic deficit levels from three aspects: language output, language reception and communication, as shown in the research results. What we need to explain here is that the above characteristics are common features in the cluster and cannot represent the language characteristics of each individual in the cluster. Similar results were also obtained in this study: spontaneous speech was correlated with naming, which had the greatest impact on WAB-AQ score.
The limitation of the current study is to include individuals with post-stroke aphasia at various stages of the disease, which increases the heterogeneity of research objects. More than 65% of individuals had WAB-AQ scores lower than two-thirds of 93.7 within 6 months after onset. The number of patients within one month, one to six months, six months to one year and more than one year accounted for 29.2%, 36.4%, 13.6% and 20.8% respectively. There are significantly fewer individuals with moderate linguistic deficit level. Perhaps this phenomenon can be explained by the different number of individuals in different post onset periods.
In the future study, we can consider the stratification of samples according to the course of disease, or include language disorders caused by other diseases, such as primary progressive aphasia. There is no correlation analysis of aphasia types in this study, which can also be considered as a direction of future research.