Clinical utility and validity of the Functional Disability Inventory among a multicenter sample of youth with chronic pain

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 (M=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 three distinct categories of disability: No/Minimal Disability, Moderate Disability and Severe Disability. Factor analysis of FDI scores revealed a two-factor solution representing vigorous Physical Activities and non-physically strenuous Daily Activities. The three-level classification system and factor structure were further explored via comparison across the four 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. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conflict of InterestThe authors have no financial or other relationship that might lead to a conflict of interest. NIH Public Access Author ManuscriptPain. Author manuscript; available in PMC 2012 July 1. In particular these findings will facilitate use of the FDI as an outcome measure in future clinical trials.Assessment of pain-related disability is an essential component in the evaluation and treatment of pediatric patients with chronic pain. The Functional Disability Inventory (FDI) [40] is one of the most widely used measures of functional impairment among children and adolescents with chronic pain, and its initial psychometric properties have been well established [3,26]. The FDI is a brief 15-item instrument originally developed to assess disability in children and adolescents with chronic abdominal pain [41,3]. Subsequently it has been used with a variety of pediatric chronic pain conditions such as fibromyalgi...

Perceived Injustice Is Associated With Pain and Functional Outcomes in Children and Adolescents With Chronic Pain: A Preliminary Examination

“…It has demonstrated reliability in several different pediatric chronic pain populations [5,23,39,61]. On a scale ranging from 0 ("no trouble at all") to 4 ("impossible"), patients indicate how much trouble they have performing normal physical and daily activities such as walking up stairs or sitting in class for a full day.…”

Functional limitations in children and adolescents suffering from chronic pain: validation and psychometric properties of the German Functional Disability Inventory (FDI-G)

“…Referring to a factor analytic study of the English version of the FDI study [22], the 15 items of the German FDI version were subjected to an exploratory factor analysis (EFA) employing principal component analysis with varimax rotation. Preliminary analyses were conducted to ensure that all assumptions (adequate sample size and correlation of items) and factorability criteria (inter-item correlation, anti-image correlation, KMO measure of sampling adequacy and Bartlett's test of sphericity) were met.…”

“…The FDI has also been used to evaluate effects of different treatment interventions for pediatric pain [20,21]. In a recent study, Kashikar-Zuck et al [22] utilized a large multicenter dataset of 1300 youths between the ages 8 and 18 years with chronic pain conditions such as head, back, abdominal and widespread pain to evaluate the psychometric properties of the FDI. In this study, a twofactor solution of the FDI constituting vigorous physical activities and non-physically strenuous daily activities was found.…”

Count up to two but not beyond

“…They use cut points established in a prior analysis of data from 1300 children with a variety of pain disorders [7]. That study set cut points at the upper and lower quartiles of the distribution to give three groups (no/minimal, moderate and severe disability) validating the classification by correlating FDI scores with pain intensity.…”

“…other measures of function.) Kashikar-Zuck et al [7] analysis of the FDI showed that mean disability increased with age and that there were slight differences between clinical groups in FDI score: information not used in Sil et alÕs analysis.…”