Use of diverse diagnostic criteria for acquired apraxia of speech: a scoping review

There is a growing body of evidence that speech and language therapy (SLT) intervention is effective in improving communication ability for individuals with non-progressive acquired apraxia of speech (AOS). However, there is no universally agreed diagnostic standard for AOS, and diverging opinions on its diagnostic features. This has led to claims that diverse diagnostic criteria may be used to select participants for AOS research studies. These claims raise concerns for evidence-based practice in AOS but have yet to be systematically investigated.

To determine the presence, nature and extent of diversity in the diagnostic criteria for non-progressive AOS used in both published studies and clinical practice internationally.

The study used a scoping review methodology that followed the 2005 framework of Arksey and O'Malley and included a consultation exercise in the form of an online survey of international SLTs. The scoping review included 157 studies involving participants with acquired AOS, published between 1997 and 2017. There were 264 respondents to the online survey of SLTs, with a completion rate of 72%. Respondents came from 15 countries and had varying levels of clinical experience.

This study found that no common set of diagnostic criteria for AOS was used universally across research and practice. Although the diagnostic criteria used to select participants with AOS were reported explicitly in most studies, they varied from study to study. Some studies used directly conflicting criteria. Use of specific diagnostic criteria in studies was influenced by year of publication but not by location. There was a trend towards increasing consistency in diagnostic criteria in recent years. Compared with the research, the survey revealed relatively greater consistency among SLTs on the speech features considered indicative of AOS, although the SLTs who responded to the survey showed variation in how diagnostic criteria were combined into sets. Use of specific diagnostic criteria was not associated with SLTs' location or experience. There were differences between the diagnostic criteria for AOS used most commonly in research studies and those selected most commonly by SLTs in the survey. These findings have implications for the generalizability of AOS research to clinical practice, as well as implications for effective research synthesis.

The claim that research and practice in the field of AOS is characterized by the use of diverse diagnostic criteria is supported by this scoping review. The findings support the need to develop a universal consensus standard for AOS diagnosis to ensure consistency across research and clinical practice.