Construction and Validation of the 4-Item Dynamic Gait Index

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Research Report Construction and Validation of the 4-Item Dynamic Gait Index Background and Purpose. People with balance disorders often have difficulty walking. The purpose of this study was to develop and test the psychometric properties of a short form of the Dynamic Gait Index (DGI) for the clinical measurement of walking function in people with balance and vestibular disorders. Subjects. A total of 123 subjects with such disorders (test subjects) and 103 control subjects were included in this study. Methods. Rasch and factor analyses were used to create a short form of the DGI. Internal consistency and discriminative validity for test subjects versus control subjects and for falling versus nonfalling test subjects were evaluated. Results. Four items were selected for the shorter version of the test: gait on level surfaces, changes in gait speed, and horizontal and vertical head turns. Discussion and Conclusion. The clinical psychometric properties of the 4-item DGI were equivalent or superior to those of the 8-item test. The 4-item DGI can be used by clinicians to measure gait in people with balance and vestibular disorders without compromising important clinical measurement characteristics. [Marchetti GF, Whitney SL. Construction and validation of the 4-item Dynamic Gait Index. Phys Ther. 2006;86:1651–1660.] Key Words: Gait, Measurement, Validity, Vestibular system. Gregory F Marchetti, Susan L Whitney Physical Therapy . Volume 86 . Number Downloaded 12 . December from http://ptjournal.apta.org/ 2006 by guest on January 11, 2014 1651
The purpose of this study was to examine the item fit, redundancy, and unidimensionality of the 8-item Dynamic Gait Index (DGI), 1 which quantifies gait characteristics in people with diagnosed balance and vestibular disorders. Tools to assess balance and gait assist health care professionals in making decisions about intervention and management. It is imperative that these tools be reliable, valid, and as concise as possible to optimize time management. Redundant items are less time efficient, without yielding additional data for clinical management. A shorter tool would be more clinically feasible and might make clinicians more likely to use the instrument. The DGI often has been used as a rehabilitation outcome measure, yet if it were easier to administer and shorter, it theoretically could be used as a screening tool. The DGI was developed for use in community-living older people and also has been used for people with balance and vestibular disorders. 2–14 The DGI is an 8-item tool with which the examiner rates an individual’s gait performance on an ordinal scale that ranges from 0 to 3. 1 Higher scores indicate better performance, with a maximal score of 24. Items on the DGI require people to modify their gait while ambulating. Interrater reliability for people with peripheral vestibular disorders has been reported to have a composite kappa of .64 and a Spearman rho of .95 for the 8-item test based on the scores of 2 raters. 12 The concurrent validity of the DGI and the Berg Balance Scale for people with central and peripheral vestibular disorders has been established, 8 and the DGI also correlates well with the Activitiesspecific Balance Confidence Scale, 4 which is a self-report scale of balance confidence. 15 Scores on the DGI of less than 20 have been related to reported falls in community-living older people 16,17 and in people with central and peripheral vestibular dysfunction. 3,5,10 The DGI has been used widely as an outcome measure and has demonstrated change over the course of a vestibular rehabilitation program. 2,3,6,7,14 It takes approximately 10 minutes or less to complete and score the DGI. If the tool could provide comparable data with fewer items, a shorter version would make the examiner more efficient. The purpose of this study was to determine whether the DGI could be shortened from its original form. We hypothesized that the use of fewer items on the DGI could provide results comparable to those of the 8-item DGI. Thus, a Rasch analysis was performed to determine whether a shorter version of the DGI could provide valid results without a loss of integrity of the tool. The items that were chosen for the shorter version of the DGI were selected on the basis of content, subject performance, clinical feasibility (time and equipment), and fit with the single construct of dynamic gait performance. Method Subjects Data from a total of 226 people were used in these analyses; the mean age of the subjects was 56.7 years (SD20.3, range14–91), and 132 (58.4%) were women. A total of 123 subjects who had balance and vestibular disorders and who were seen in a tertiary-care clinic for balance disorders represented the test subjects; the mean age was 62.3 years (SD16.3, range14–91), and 75 (61%) were women. A total of 103 people without vestibular and balance dysfunction represented the control subjects; the mean age was 50.0 years (SD22.5, range21–84); 57 (55%) were women. All control subjects provided written informed consent. The test group was significantly older than the control group GF Marchetti, PT, PhD, is Assistant Professor, Department of Physical Therapy, Duquesne University, Pittsburgh, Pa, and Assistant Professor, Department of Otolaryngology, University of Pittsburgh, Pittsburgh, Pa. SL Whitney, PT, PhD, NCS, ATC, is Associate Professor, Departments of Physical Therapy and Otolaryngology, University of Pittsburgh, 6035 Forbes Tower, Pittsburgh, PA 15260 (USA), and Program Director, Physical Therapy Department, Centers for Rehab Services, University of Pittsburgh Medical Center, Pittsburgh, Pa. Address all correspondence to Dr Whitney at: whitney@pitt.edu. Both authors provided concept/idea/research design, writing, and facilities/equipment. Dr Marchetti provided data analysis. Dr Whitney provided data collection, project management, fund procurement, subjects, and institutional liaisons. This study was approved by the institutional review board of the University of Pittsburgh. This project was supported, in part, by National Institutes of Health grants DC 05384 (to Dr Whitney), AG10009, and R01 AG14116. A portion of these data were presented at the Combined Sections Meeting of the American Physical Therapy Association; February 3, 2006; San Diego, Calif. This article was received December 29, 2005, and was accepted July 24, 2006. DOI: 10.2522/ptj.20050402 1652 . Marchetti and Whitney Downloaded from http://ptjournal.apta.org/ by guest Physical on January Therapy 11, . Volume 2014 86 . Number 12 . December 2006
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Construction and Validation of the 4-Item Dynamic Gait Index

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