ArticleClinical utility and validity of the Functional Disability Inventory among a multicenter sample of youth with chronic painKashikar-Zuck, Susmitaa,*; Flowers, Stacy R.a; Claar, Robyn Lewisb; Guite, Jessica W.c; Logan, Deirdre E.b; Lynch-Jordan, Anne M.a; Palermo, Tonya M.d; Wilson, Anna C.e Author Information Sponsorships or completing interests that may be relevant to content are disclosed at the end of this article. aDivision of Behavioral Medicine and Clinical Psychology, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, OH, USA bDivision of Pain Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, and Department of Psychiatry, Children’s Hospital Boston and Harvard Medical School, Boston, MA, USA cDepartment of Anesthesiology and Critical Care Medicine, The Children’s Hospital of Philadelphia and The University of Pennsylvania School of Medicine, Philadelphia, PA, USA dDepartments of Anesthesiology, Pediatrics, and Psychiatry, University of Washington School of Medicine, Seattle, WA, USA eDepartments of Pediatrics, Anesthesiology and Perioperative Medicine, Oregon Health and Science University, Portland, OR, USA *Corresponding author. Address: Division of Behavioral Medicine and Clinical Psychology, MLC 3015, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA. Tel.: +1 513 636 6337; fax: +1 513 636 0602. E-mail address:[email protected] Article history: Received 1 November 2010; Received in revised form 9 February 2011; Accepted 25 February 2011. Pain 152(7):p 1600-1607, July 2011. | DOI: 10.1016/j.pain.2011.02.050 Buy Metrics Abstract The Functional Disability Inventory (FDI) is a well-established and commonly used measure of physical functioning and disability in youth with chronic pain. Further validation of the measure has been called for, in particular, examination of the clinical utility and factor structure of the measure. To address this need, we utilized a large multicenter dataset of pediatric patients with chronic pain who had completed the FDI and other measures assessing pain and emotional functioning. Clinical reference points to allow for interpretation of raw scores were developed to enhance clinical utility of the measure, and exploratory factor analysis was performed to examine its factor structure. Participants included 1300 youth ages 8 to 18 years (mean = 14.2 years; 76% female) with chronic pain. Examination of the distribution of FDI scores and validation with measures of depressive symptoms and pain intensity yielded 3 distinct categories of disability: No/Minimal Disability, Moderate Disability, and Severe Disability. Factor analysis of FDI scores revealed a 2-factor solution representing vigorous Physical Activities and non-physically strenuous Daily Activities. The 3-level classification system and factor structure were further explored via comparison across the 4 most commonly encountered pain conditions in clinical settings (head, back, abdominal, and widespread pain). Our findings provide important new information regarding the clinical utility and validity of the FDI. This will greatly enhance the interpretability of scores for research and clinical use in a wide range of pediatric pain conditions. In particular, these findings will facilitate use of the FDI as an outcome measure in future clinical trials. Clinical reference points and a preliminary factor structure for the Functional Disability Inventory (FDI) increase the clinical and research utility of the measure. © 2011 Lippincott Williams & Wilkins, Inc.