Apraxia

Clinical Rehabilitation 2007; 21: 760–767

Apraxia of speech: how reliable are speech and language therapists’ diagnoses?
Katharyn Mumby Central Cheshire PCT, now at School of Education, Communication and Language Sciences, University of Newcastle upon Tyne, Audrey Bowen School of Psychological Sciences, University of Manchester and Anne Hesketh School of Psychological Sciences, University ofManchester, Manchester, UK Received 23rd June 2006; returned for revisions 8th November 2006; revised manuscript accepted 15th December 2006.

Objective: To discover how reliably speech and language therapists could diagnose apraxia of speech using their clinical judgement, by measuring whether they were consistent (intra-rater reliability), and whether their diagnoses agreed (inter-raterreliability). Design: Video clips of people with communication difficulties following stroke were rated by four speech and language therapists who were given no definition of apraxia of speech, no training, and no opportunity for conferring. Settings: Videos were made of people following stroke in their homes. Ratings of the videos were carried out in the university lab under controlled conditions.Subjects: Forty-two people with communication difficulties such as aphasia, apraxia of speech and dysarthria took part, and four specialist speech and language therapists acted as raters. Main measure: Speech and language therapists’ ratings of the presence and severity of apraxia of speech using videos. Results: Intra-rater reliability was high for diagnosing (1) the presence of apraxia of speech(Cohen’s kappas ranging from 0.90 to 1.00; 0.93 overall), and (2) the severity of apraxia of speech (kappa 0.84 to 0.92; 0.90 overall). The inter-rater reliability was also high for both the presence of apraxia of speech (kappa 0.86) and severity of apraxia of speech (0.74). Conclusion: Despite controversy over its nature and existence, specialist speech and language therapists show high levels ofagreement on the diagnosis of apraxia of speech using their clinical judgement.

Introduction
Apraxia of speech is a communication impairment that can occur following stroke, but there is considerable controversy in the literature about how to define and assess it in order to tailor rehabilitation.

Address for correspondence: Anne Hesketh, HCD, School of Psychological Sciences, Humanities DevasStreet Building, University of Manchester, Oxford Road, Manchester M13 9PL, UK. e-mail: anne.hesketh@manchester.ac.uk © SAGE Publications 2007 Los Angeles, London, New Delhi and Singapore

In apraxia of speech, speech sounds are made in an effortful or erratic way in the absence of muscle weakness. Traditionally this has been thought of as a disorder of motor programming,1 but there has been heateddebate over the last 30 years about its true nature.2,3 Currently there is no universally agreed definition of apraxia of speech or ‘gold standard’ for assessment. Definitions of apraxia of speech have been evolving within different theoretical frameworks: behavioural, cognitive and neuroanatomical4 and also within acoustic and phonetic-perceptual frameworks.5 However, it is unclear to what extent10.1177/0269215507077285

Diagnosing apraxia of speech each framework is useful in differential diagnosis with other communication impairments such as aphasia and dysarthria. Other recent major reviews6–8 have highlighted how difficult it is to interpret the existing studies in the field because of the failure to describe subject selection adequately. Apraxia of speech is known to co-occur withaphasia, which may also result in sound errors in speech, aphasic ‘phonemic paraphasias’, involving the selection and production of the wrong phoneme or speech sound (e.g. ‘t’ in ‘speat’, when the target word was ‘speak’). Their errors might be described as the wrong sound easily articulated. The sound errors characteristic of apraxia of speech on the other hand tend to involve articulatory...