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Pain Research and Treatment
Volume 2012 (2012), Article ID 621619, 15 pages
http://dx.doi.org/10.1155/2012/621619
Clinical Study

Validation of the Self-Assessment of Treatment Questionnaire among Patients with Postherpetic Neuralgia

1United BioSource Corporation, 7101 Wisconsin Avenue, Suite 600, Bethesda, MD 20814, USA
2Astellas Pharma Global Development, 2350 AC Leiderdorp, The Netherlands
3Astellas Pharma Global Development, Middlesex TW18 3AZ, UK
4United BioSource Corporation, London W6 7HA, UK

Received 22 March 2012; Revised 5 June 2012; Accepted 27 June 2012

Academic Editor: Jarred Younger

Copyright © 2012 Kathleen W. Wyrwich et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Introduction. A five-item Self-Assessment of Treatment (SAT) was developed to assess improvement and satisfaction with treatment associated with the application of a novel high concentration 8% capsaicin topical patch in clinical trials in patients with postherpetic neuralgia (PHN). This study evaluated the item performance and psychometric properties of the SAT. Methods. The SAT, Brief Pain Inventory, SF-36v2, Short-Form McGill Pain Questionnaire, and Patient and Clinician Global Impression of Change (PGIC; CGIC) scores were measured in two 12-week Phase 3 clinical trials. Factor analysis assessed the underlying factor structure, followed by examination of the reliability and validity of the multi-item domain. Results. Pooled data from 698 patients completing SAT after 12 weeks of treatment were analyzed. A one-factor model combining three of the five items emerged as the optimal solution. Internal consistency reliability of this treatment efficacy factor was high (Cronbach's alpha = 0.89). Construct validity was demonstrated by moderate to high correlations with change in other study endpoints. SAT mean scores consistently discriminated between patient change groups defined by PGIC and CGIC. Conclusions. The measurement properties of the three-item version of SAT are valid and reliable for assessment of treatment with a high concentration capsaicin patch among patients with PHN.