title: Development and validation of the Diabetic Peripheral Neuropathic Pain Impact (DPNPI) measure, a patient-reported outcome measure.
abstract: OBJECTIVE
  Diabetic peripheral neuropathy (DPN) occurs in 26-47 % of diabetes patients and may have negative impacts on physical functioning, sleep, well-being, and quality of life. The Diabetic Peripheral Neuropathic Pain Impact measure (DPNPI) was developed to measure disease impacts and treatment effects. Presented are the DPNPI conceptual development and validation findings.
  
  
  METHODS
  The DPNPI was developed following the FDA Guidance for Industry on patient-reported outcome (PRO) measures. Concept elicitation (CE) included literature review, clinical expert interviews, and patient interviews/focus groups. Qualitative data were analyzed following grounded theory principles, and draft items were cognitively debriefed. The measure underwent psychometric validation, and an a priori statistical analysis plan assessed the measurement model, reliability, and validity. Simultaneous analyses of item functioning were conducted using Rasch measurement theory (RMT). All tests were performed for the total score and each domain.
  
  
  RESULTS
  Twenty-five patients and three clinical experts participated in CE which resulted in a 27-item validation ready measure. In the validation study (N = 124), nine draft items were dropped due to high missing data and/or high correlations between items. Factor analysis revealed three domains: physical functioning/mobility, sleep, and daily activities. RMT confirmed adequate item fit and placement within domains. Internal consistency ranged from 0.91 to 0.96 and test-retest from 0.84 to 0.91. All prespecified hypotheses for convergent and discriminant validity were met.
  
  
  CONCLUSIONS
  CE and psychometric results provide evidence that the final, 18-item DPNPI is a reliable and valid PRO measure of disease impacts and treatment for DPNP. Further validation work should include responsiveness assessment.
authors.affiliation: The Brod Group, 219 Julia Avenue, Mill Valley, CA, 94941, USA. mbrod@thebrodgroup.net.
authors.forename: Meryl
authors.initials: M
authors.lastname: Brod
authors.affiliation: GlaxoSmithKline, 2301 Renaissance Blvd., King of Prussia, PA, 19406, USA.
authors.forename: Steven I
authors.initials: SI
authors.lastname: Blum
authors.affiliation: Health Research Associates, Inc., 6505 216th Street SW, Suite 105, Mountlake Terrace, WA, 98043, USA.
authors.forename: Donald M
authors.initials: DM
authors.lastname: Bushnell
authors.affiliation: Actavis, Inc., Harborside Financial Center, Plaza V, Jersey City, NJ, 07311, USA.
authors.forename: Abhilasha
authors.initials: A
authors.lastname: Ramasamy
mesh_terms: D000328:Adult; D000368:Aged; D000068598:Data Accuracy; D003929:Diabetic Neuropathies / Q000175:diagnosis*; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D063868:Patient Outcome Assessment; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life / Q000523:psychology*; D011795:Surveys and Questionnaires
keywords: Adult functioning and well-being; Diabetic peripheral neuropathic pain; Patient-reported outcomes; Psychometrics