Self- and surrogate-reported communication functioning in aphasia.

PURPOSE: To evaluate the dimensionality and measurement invariance of the aphasia communication outcome measure (ACOM), a self- and surrogate-reported measure of communicative functioning in aphasia. METHODS: Responses to a large pool of items describing communication activities were collected from 133 community-dwelling persons with aphasia of ≥ 1 month post-onset and their associated surrogate respondents. These responses were evaluated using confirmatory and exploratory factor analysis. Chi-square difference tests of nested factor models were used to evaluate patient-surrogate measurement invariance and the equality of factor score means and variances. Association and agreement between self- and surrogate reports were examined using correlation and scatterplots of pairwise patient-surrogate differences. RESULTS: Three single-factor scales (Talking, Comprehension, and Writing) approximating patient-surrogate measurement invariance were identified. The variance of patient-reported scores on the Talking and Writing scales was higher than surrogate-reported variances on these scales. Correlations between self- and surrogate reports were moderate-to-strong, but there were significant disagreements in a substantial number of individual cases. CONCLUSIONS: Despite minimal bias and relatively strong association, surrogate reports of communicative functioning in aphasia are not reliable substitutes for self-reports by persons with aphasia. Furthermore, although measurement invariance is necessary for direct comparison of self- and surrogate reports, the costs of obtaining invariance in terms of scale reliability and content validity may be substantial. Development of non-invariant self- and surrogate report scales may be preferable for some applications.

Patient-reported cognitive and communicative functioning: 1 construct or 2?

OBJECTIVES: To examine the dimensionality of scales for measuring patient-reported cognitive and communicative functioning in a sample of stroke survivors and to evaluate the consequences for measurement of treating them as a single, undifferentiated construct. DESIGN: Secondary analysis of existing cross-sectional data. SETTING: Data were collected in outpatient rehabilitation clinics and in the community. PARTICIPANTS: Unilateral stroke survivors (N=316) 3 months or more postonset referred for participation in research. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The Burden of Stroke Scale cognition and communication domain scales were evaluated by using confirmatory factor analysis, Rasch analysis, and tests of differential item functioning (DIF). To evaluate the impact of multidimensionality on the measurement of individual patients, separately estimated cognition and communication scores were compared. Combined and separately estimated scores were also examined for responsiveness to group differences in the presence of cognitive and communicative impairment. RESULTS: Factor analysis and Rasch model fit analyses equivocally supported the unidimensionality of the item pool. DIF analyses between participants with right versus left hemisphere stroke suggested multidimensionality. Scaling cognition and communication items separately resulted in different person scores for a significant number of patients and greater responsiveness to group differences. CONCLUSIONS: Patient-reported scales assessing communication along with more general cognitive activities may possess an internal structure that is inconsistent with a unidimensional measurement model with potential negative consequences for measurement.

Effects of feedback frequency and timing on acquisition, retention, and transfer of speech skills in acquired apraxia of speech.

PURPOSE: Two studies examined speech skill learning in persons with apraxia of speech (AOS). Motor-learning research shows that delaying or reducing the frequency of feedback promotes retention and transfer of skills. By contrast, immediate or frequent feedback promotes temporary performance enhancement but interferes with retention and transfer. These principles were tested in the context of a common treatment for AOS. METHOD: Two studies (N = 4, N = 2) employed single-subject treatment designs to examine acquisition and retention of speech skills in adults with AOS under different feedback conditions. RESULTS: Reduced-frequency or delayed feedback enhanced learning in 3 participants with AOS. Feedback manipulation was not an influential variable in 3 other cases in which stimulus-complexity effects may have masked treatment effects. CONCLUSIONS: These findings demonstrate that individuals with AOS can benefit from structured intervention. They provide qualified support for reduction and delay of feedback, although interaction with other factors such as stimulus complexity or task difficulty needs further exploration. This study adds to the growing body of literature investigating the use of principles of motor learning in treating AOS and provides impetus for consideration of pre-treatment variables that affect outcome in treatment studies.

Principles of motor learning in treatment of motor speech disorders.

PURPOSE: There has been renewed interest on the part of speech-language pathologists to understand how the motor system learns and determine whether principles of motor learning, derived from studies of nonspeech motor skills, apply to treatment of motor speech disorders. The purpose of this tutorial is to introduce principles that enhance motor learning for nonspeech motor skills and to examine the extent to which these principles apply in treatment of motor speech disorders. METHOD: This tutorial critically reviews various principles in the context of nonspeech motor learning by reviewing selected literature from the major journals in motor learning. The potential application of these principles to speech motor learning is then discussed by reviewing relevant literature on treatment of speech disorders. Specific attention is paid to how these principles may be incorporated into treatment for motor speech disorders. CONCLUSIONS: Evidence from nonspeech motor learning suggests that various principles may interact with each other and differentially affect diverse aspects of movements. Whereas few studies have directly examined these principles in speech motor (re)learning, available evidence suggests that these principles hold promise for treatment of motor speech disorders. Further research is necessary to determine which principles apply to speech motor (re)learning in impaired populations.

The Aphasia Communication Outcome Measure (ACOM): Dimensionality, Item Bank Calibration, and Initial Validation.

PURPOSE: The purpose of this study is to investigate the structure and measurement properties of the Aphasia Communication Outcome Measure (ACOM), a patient-reported outcome measure of communicative functioning for persons with aphasia. METHOD: Three hundred twenty-nine participants with aphasia responded to 177 items asking about communicative functioning. The data were analyzed using a categorical item factor analysis approach. Validity of ACOM scores on the basis of their convergence with performance-based, clinician-reported, and surrogate-reported assessments of communication was also assessed. RESULTS: Fifty-nine items that obtained adequate fit to a modified bifactor measurement model and functioned similarly across several demographic and clinical subgroupings were identified. The factor model estimates were transformed to item response theory graded response model parameters, and the resulting score estimates showed good precision and moderately strong convergence with other measures of communicative ability and functioning. A free software application for administration and scoring of the ACOM item bank is available from the first author. CONCLUSIONS: The ACOM provides reliable measurement of patient-reported communicative functioning in aphasia. The results supported the validity of ACOM scores insofar as (a) factor analyses provided support for a coherent measurement model, (b) items functioned similarly across demographic and clinical subgroups, and (c) scores showed good convergence with measures of related constructs.