Towards the development and validation of an isiXhosa tool for the assessment of apraxia speech in adults: A descriptive study

Allie, Nasreen

Towards the development and validation of an isiXhosa tool for the assessment of apraxia speech in adults: A descriptive study

Thesis / Dissertation

2024

Publisher

University of Cape Town

Department

Division of Communication Sciences and Disorders

Faculty

Faculty of Health Sciences

Abstract

South Africa is a culturally and linguistically diverse country. Serving isiXhosa speakers is a challenge for many Speech-Language Pathologists as there is a lack of appropriate assessment tools for this population. Current methods of adapting existing English tools are not appropriate as this does not allow the isiXhosa linguistic features to be assessed. Changing the method of scoring renders the tool invalid and unreliable. This project consisted of 3 sequential studies based in an exploratory quantitative framework. Each study has its own methodology and sub-aims with the overall aim to develop and determine the validity and reliability of isiXhosa speech stimuli for the assessment of Apraxia of Speech (AOS) in adults. Study 1 aimed to describe and generate criteria and corresponding speech stimuli for an assessment of AOS in isiXhosa. IsiXhosa has distinguishing linguistic features – such as additional phonemes, alternate places and manners of articulation (e.g. ejectives), as well as phonetic features unique to the language (e.g. prenasalised consonants and tonal contrasts). Inclusion of these features were considered to be important in the creation of the tool. Study 2 aimed to determine the face, content and construct validity of the generated criteria and speech stimuli. The speech stimuli which consisted of words, phrases and sentences were found to be culturally appropriate and to have face, content and construct validity as judged by a group of isiXhosa speakers and a Delphi panel. The speech stimuli met the criteria for an assessment of AOS as set out in Study 1. Study 3 assessed the theoretical constructs outlined in Study 1 and Study 2 determined whether the revised criteria, which generated the newly devised speech stimuli, was valid and reliable in diagnosing AOS. The speech stimuli were based on criteria for the assessment of AOS and considered the isiXhosa linguistic features. There was high inter-rater reliability (79.2 – 98.4%) for determining the presence of features of AOS. Many of the error patterns displayed were similar to that documented in the literature for AOS, such as a higher number of errors were present on less frequently used speech stimuli and stimuli with an increasing number of syllables. It was it was hypothesized that the differences in the language such as clicks and tonal contrasts may add to complexity. Clicks presented with a higher number of errors whereas tonal contrasts had fewer errors suggesting tone was less affected by AOS. Results further suggested that the first consonant of the stimulus rather than the initial phoneme in words add to complexity in isiXhosa. Further research in this area and refinement of the speech stimuli are required to create a comprehensive tool for assessment of AOS in adults.