29th Annual RESNA Conference Proceedings

AAC Assessment Outcomes for Individuals with Developmental Disabilities

Katya Hill, Ph.D.
University of Pittsburgh


Results are presented for a retrospective study examining outcomes for clients with developmental disabilities who received a comprehensive assessment for augmentative and alternative communication (AAC) through a university clinic. Data are reported summarizing client demographics, length of evaluation, preferred AAC system features, quantitative communication performance measures, user satisfaction, and disuse and upgrade rates. Results contribute to outcomes data needed to support an evidence-based orientation to making clinical decisions during the AAC assessment process.


Augmentative and alternative communication (AAC), assessment, outcomes, evidence-based practice


Documenting outcomes to demonstrate accountability is essential for evaluating the quality and effectiveness of Augmentative and Alternative Communication (AAC). Several critical issues surround the delivery of AAC assessment service such as access to AAC services, resource and management restrictions, funding difficulties, and the abandonment of recommended AAC technologies (1). Outcomes data that summarize results achieved provide evidence to guide policy and procedure decisions.

Currently minimal outcomes data specific to AAC assessment recommendations are available to support clinical decision-making. Even less outcomes data can be found that are broken down by diagnostic categories of clients who rely on AAC interventions. A significant number of individuals who rely on AAC have been diagnosed with developmental disabilities and/or mental retardation. Clients with developmental disabilities are receiving primary services through early intervention programs, public schools, and adult rehabilitation service agencies. However, the model and extent of AAC service delivery varies widely with little outcomes data reported for achieved AAC results.

Outcomes measurement provides service deliverers with a method of providing information relating to numerous essential parameters of service delivery. The five most typically characterized dimensions are: (1) clinical results, (2) functional status, (3) quality of life, (4) satisfaction, and (5) cost (1). Third party payers want to know that AAC devices and services are worth the cost. Outcomes relating to long-term effectiveness of AAC technologies are essential. Receiving funding from third-party sources such as Medicare and Medicaid can be quite complex. Major funding sources may not be reimbursing adequately for the length of time needed to conduct AAC evaluations that lead to long-term effective use of AAC interventions. Evidence related to AAC outcomes, especially for populations typically overlooked as qualifying or benefiting from technology, is critical to support clinical decision-making and the establishment of policy and procedures (2).


  1. What is the demographic make-up of clients with developmental disabilities being referred for a comprehensive AAC assessment?
  2. What was the length of time needed to complete an AAC assessment?
  3. What were the AAC systems recommended and what were the preferred AAC system features?
  4. Are the recommended AAC systems still used and what outcomes were measured to monitor the effectiveness of communication?
  5. How does the client/family perceive the value of the AAC systems and treatments.


An archival data review was conducted using client files for 24 clients diagnosed with developmental disabilities that attended the University clinic at Edinboro University of Pennsylvania from 1999 to 2004. The diagnosis for all clients included at least one report of mental retardation with ranges of mild to profound. The archival data review and follow-up contact were conducted one to five years post assessment. The archival data sources utilized included client files (evaluation reports, progress reports, AAC performance reports, and funding requests) and phone or personal interviews.


The data from this study have been organized by research question.

1. Clinic records showed that 24 clients with a diagnosis of developmental disabilities were referred to a University clinic for a comprehensive AAC assessment. Records indicated that the diagnosis included mild-moderate mental retardation for 19 clients and severe-profound mental retardation for 5 clients. Gender statistics showed that 64% were male and 36% were female. They ranged in age from toddlers (2.5 years old) to adult (50 years old). Clients were receiving educational and social services from a variety of agencies, which included 34% receiving preschool services, 46% special education services in the public schools, and 20% were being serviced through community mental retardation programs for adults.

2. The length of time needed to complete an AAC assessment ranged from 1 to 10 hours (one to five diagnostic sessions) with an average of 6.5 hours to complete a comprehensive AAC assessment. The only evaluations that were limited to one session or 60 minutes were preschool-aged children with severe-profound mental retardation indicated in their referral. Assessment times above the mean of 6.5 hours involved clients requiring decisions about alternative access methods.

3. Of the 24 clients, 19 (79%) received recommendations for a high technology AAC system. Only 2 clients (8%) were not recommended advancing to a light technology or high performance AAC system with the report recommendations indicating to continue with the current unaided and aided low technology AAC interventions. Recommended voice output AAC interventions consisted of 13% for digitized light technology and 79% for synthesized high technology. High technology AAC interventions recommended indicated that 53% of the systems represented language using single-meaning pictures and 47% of the systems represented language using symbols with multiple meanings and sequencing (semantic compaction). Records showed that 37% of the systems had full grid-type touch screens while 63% of the systems provided a hybrid (static and touch screen) display.

4. Of the 19 clients who received high technology AAC systems, only 1 preschool client is no longer using the device, due to improvements in natural speech after four years with the system. The other clients continue to use the original AAC system purchased, with 26% of the clients upgrading to a more advanced level of the language application program. The top four performance measures used to monitor progress and measure communication competence during trials were: 1) frequency of use of spontaneous utterances (and pre-stored messages); 2) frequency of use of language representation methods; 3) frequency of core vocabulary; and 4) Mean Length of Utterance in words.

5. Social validation data indicates high customer satisfaction with the AAC assessment process, recommendations, and AAC system. Interview data revealed the following: 1) 100% of family members and/or agency staff strongly agreed that the AAC assessment was comprehensive and that the time needed was appropriate for the AAC device selection process; 2) all family members strongly agreed that the AAC assessment took into consideration a range and variety of AAC interventions and solutions to meet communication needs; 3) all family members strongly agreed that language activity monitoring (LAM) was valued and contributed to selecting an AAC system; 4) all family members strongly agreed that their values regarding communication, technology, and future goals were considered during the assessment; 5) agency staff members agreed that the recommended AAC systems could be supported in the client's daily environment.


Weaknesses of this study must be considered such as small sample size and the retrospective design of the study. Certain variables could not be controlled because they occurred in the past. However, even considering these deficits, these data provide important insights into several of the outcomes methods relating to the AAC assessment process and service delivery.

The data reveal that across the age ranges individuals with developmental disabilities benefit from using high performance AAC systems. Providing a hierarchical approach to recommending and funding AAC systems based on the range of technology rather than language considerations can not be supported by these data. Rather, the clients from this study achieved functional communication goals using multiple language representation methods to support single word vocabulary for spontaneous message construction. High technology AAC systems provided the features and flexibility that allowed clients to maximize potential.

Evidence-based rehabilitation services require that the client defines the outcomes that are most important to his or her functioning (3). AAC assessments confined to the hours allowed by reimbursement rates may not provide the time needed for clients with mental retardation to participant in defining or measuring outcomes, and, therefore, would not be in the best interest of the client. These data suggest that when the interest of the client is held paramount in the evaluation process, individuals with developmental disabilities may frequently exceed expectations about possible communication outcomes.


(1) DeRuyter, Frank (1995). Evaluating outcomes in assistive technology: Do we understand the commitment? Assistive Technology, 7 (1), 3-8.

(2) Hill, K., Spurk, E., & Sunday, J. (2004). A study of AAC intervention outcomes for a university clinic. Poster presented at the 2004 ASHA Annual Convention, Philadelphia, Pa, November 2004.

(3) Pollock, N., & Rochon, S. (2002). Becoming an evidence-based practitioner. In M. Law (Ed.) Evidence-based rehabilitation: A guide to practice. Thorofare, NJ: Slack Inc.

Katya Hill, Ph.D., CCC-SLP
Associate Professor
Communication Science and Disorders
4033 Forbes Tower
University of Pittsburgh
Pittsburgh, PA 15260


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