Portland State University. Department of Speech Communication
Mary E. Gordon
Date of Publication
Master of Science (M.S.) in Speech with Emphasis in Speech Pathology
1 online resource (59 p.)
The term "developmental apraxia of speech" (DAS) has been a confusing one since Morley, Court and Miller (1954) first applied it to articulatory patterns of a specific group of children. Until recently, the differentiation of diagnostic features of DAS in children as compared to other articulatory disorders has been difficult. One evaluation tool, developed by Blakeley (1980), to assist in differential diagnosis of DAS is the Screening Test for Developmental Apraxia of Speech (STDAS). This study examined the validity of this tool by comparing its results with the evaluations by three Speech-Language Pathologists knowledgeable in the area of developmental and/or acquired apraxia of speech.
Twenty subjects, ranging in age from 4-5 to 7-7 years, participated in this study. The subjects were independently screened by four evaluators. The first evaluation was conducted by this researcher, administering the STDAS to each subject. The other three evaluators screened each subject using their own procedures, excluding the STDAS. The STDAS resulted in a probability rating for DAS. The three evaluators were instructed to rate each subject on probability of DAS based upon their individual methods of assessment. To determine the relationship between the three evaluator pairs (BC, BD, CD) the index of association used was the Pearson Product - Moment Correlation Coefficient (Pearson-r). The results indicated the evaluators only slightly agreed with one another. Although they were in general agreement as to what characteristics constitute DAS, their perceptions of each subject were quite varied.
In correlating the STDAS (A) with each evaluator (B, C, D) using the Pearson-r, the results ranged from slight correlation of AB (.20) to high correlation of AD (.73). This outcome may indicate that the STDAS tapped more of the components of apraxia (in the sense of comprehensiveness) than any single evaluator measure.
Two factors seemed to contribute to the varied results among evaluators: (1) lack of information about the subjects' history of development, including familial history and management history; and (2) varied amount of structure used among the evaluators. When comparing the STDAS results with an evaluator who used a highly structured method of assessment, the correlation was high. This evaluator had the advantage of objective data, as well as clinical judgment upon which to base the final rating for each subject.
The inconsistency among the evaluators' assessment results is an excellent argument for a screening instrument that uses the current body of knowledge concerning DAS. The STDAS forces the examiner to assess the child more objectively. The resulting data of this study support Blakeley's intention for the STDAS to be used as part of a differential diagnosis of DAS. When combined with other measures, such as case history, clinical judgment and neurological assessment, the STDAS can play an important contributing role in differentiating DAS from other articulatory disorders.
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Thorsen, Deborah L., "A validation study of the screening test for developmental apraxia of speech" (1984). Dissertations and Theses. Paper 3331.