Use of the Progressive Aphasia Severity Scale (PASS) in monitoring speech and language status in PPA

Primary progressive aphasia (PPA) is a devastating neurodegenerative syndrome involving the gradual development of aphasia, slowly impairing the patient's ability to communicate. Pharmaceutical treatments do not currently exist and intervention often focuses on speech-language behavioral therapies, although further investigation is warranted to determine how best to harness functional benefits. Efforts to develop pharmaceutical and behavioral treatments have been hindered by a lack of standardized methods to monitor disease progression and treatment efficacy.

Here we describe our current approach to monitoring progression of PPA, including the development and applications of a novel clinical instrument for this purpose, the Progressive Aphasia Severity Scale (PASS). We also outline some of the issues related to initial evaluation and longitudinal monitoring of PPA.

In our clinical and research practice we perform initial and follow-up assessments of PPA patients using a multi-faceted approach. In addition to standardized assessment measures, we use the PASS to rate presence and severity of symptoms across distinct domains of speech, language, and functional and pragmatic aspects of communication. Ratings are made using the clinician's best judgment, integrating information from patient test performance in the office as well as a companion's description of routine daily functioning.

Monitoring symptom characteristics and severity with the PASS can assist in developing behavioral therapies, planning treatment goals, and counseling patients and families on clinical status and prognosis. The PASS also has potential to advance the implementation of PPA clinical trials.

PPA patients display heterogeneous language profiles that change over time given the progressive nature of the disease. The monitoring of symptom progression is therefore crucial to ensure that proposed treatments are appropriate at any given stage, including speech-language therapy and potentially pharmaceutical treatments once these become available. Because of the discrepancy that can exist between a patient's daily functioning and standardized test performance, we believe a comprehensive assessment and monitoring battery must include performance-based instruments, interviews with the patient and partner, questionnaires about functioning in daily life, and measures of clinician judgment. We hope that our clinician judgment-based rating scale described here will be a valuable addition to the PPA assessment and monitoring battery.