Factor analysis of signs of childhood apraxia of speech

Purpose
To investigate the latent factors underlying signs of childhood apraxia of speech (CAS) in a group of 57 children with CAS.

Method
The speech of 57 children with CAS (aged 3;5–17;0) was coded for signs of CAS. All participants showed at least five signs of CAS and were judged to have CAS by speech pathologists experienced in pediatric speech disorders. Participants were selected to represent a range of severity of CAS: 30 children were verbal and 27 were minimally verbal with comorbid autism. Participants’ scores for each sign (the number of times that sign appeared during a child’s speech sample) were converted to z-scores, then entered as variables into an exploratory factor analysis. Models were compared using the Akaike Information Criterion (AIC).

Results
The three-factor model had the lowest AIC and best fit the data. After oblique rotation, syllable segmentation, slow rate, and stress errors loaded most highly on Factor 1. Groping, addition of phonemes other than schwa, and difficulty with coarticulation loaded most highly on Factor 2. Variable errors loaded most highly on Factor 3. Thus, factors were interpreted as being associated with (1) prosody, (2) coarticulation, and (3) inconsistency.

Conclusions
Results are consistent with the three consensus criteria for CAS from the American Speech-Language-Hearing Association: Inappropriate prosody, disrupted coarticulatory transitions, and inconsistent errors on repeated tokens. High loading of the syllable segmentation sign on the inappropriate prosody factor also supports the use of a pause-related biomarker for CAS.