Lower Extremity Prosthetic Mobility: A Comparison of 3 Self-Report Scales William C. Miller, PhD, MSc, A. Barry Deathe, MD, Mark Speechley, PhD ABSTRACT. Miller WC, Deathe AB, Speechley M. Lower extremity prosthetic mobility: a comparison of 3 self-report scales. Arch Phys Med Rehabil 2001;82:1432-40. Objective: To assess and compare the reliability and validity of the Houghton Scale, the Prosthetic Profile of the Amputee Locomotor Capabilities Index (PPA-LCI), and the Prosthetic Evaluation Questionnaire (PEQ) mobility subscale, 3 disease- specific self-report measures of functional mobility for lower extremity prosthetic mobility. Design: Four-week test-retest: 1 sample for reliability anal- yses, 1 sample for validity analyses. Setting: University-affiliated outpatient amputee clinic, in Ontario, Canada. Participants: Two outpatient amputee samples (sample 1 [n = 55], for reliability analysis; sample 2 [n = 329], for validity analysis). Interventions: Not applicable. Main Outcome Measures: Test-retest of reliability and convergent validity of the 3 scales. Convergent validity and discriminative ability were also assessed after setting a priori hypotheses for 2 scales of walking performance, balance con- fidence, and other indicators of ambulatory ability. Results: The reliability of the PPA-LCI (intraclass correla- tion coefficient [ICC] = .88) was slightly higher than the Houghton Scale (ICC = .85) and the PEQ mobility subscale (ICC = .77). The PPA-LCI was prone to high ceiling effects (40%) that would limit its ability to detect improvement. Evi- dence for convergent validity, when compared with the 2-Minute Walk Test, Timed Up and Go, and the Activity- Specific Balance Confidence Scale, was supported as hypoth- esized in all the scales. Each of the scales was able to discrim- inate between different groups for amputation cause, walking distance, mobility device use, and automatism, with each hav- ing varying strength related to relative precision. The Hough- ton Scale was the only scale able to distinguish between am- putation levels. Conclusions: Reliability and validity of all the scales are acceptable for group level comparison. None of the scales had clearly superior psychometric properties compared with the others. Further research is required to assess responsiveness. Key Words: Amputees; Artificial limbs; Leg; Psychomet- rics; Rehabilitation; Reproducibility of results. © 2001 by the American Congress of Rehabilitation Medi- cine and the American Academy of Physical Medicine and Rehabilitation R EHABILITATION PRACTITIONERS and researchers need measures that can distinguish among levels of dis- ability, predict prognosis, help plan patient care, and indicate change in functional status occurring as a result of intervention. The demand for accountability comes not only from funding sources but also from the recipients of treatment. Many factors complicate the issue of measurement in rehabilitation. Measur- ing disability, for instance, is prone to wide disagreement about what should be measured and what is the best method to capture the information. 1-3 In addition, there is the tendency among researchers to create new measures rather than to refine existing instruments. 4 Fifteen years ago, Keith 2 lamented the state of measurement and evaluation in rehabilitation, which continues today, 3 despite the fact that assessment of function has become more sophisticated. Measuring the outcomes of rehabilitation of persons who have had a lower extremity amputation is a good example of the measurement dilemma faced in other areas of rehabilita- tion. Successful outcome among amputees is multifaceted and can vary, depending on the goals of the individual. Although no consensus exists on which measures should be used, most investigators advocate that a variety of outcomes relating to quality of life, including measurement of functional limitation, should be considered. 5 Although community reintegration and generally improved mobility are the ultimate goals of amputee rehabilitation pro- grams, prosthetic mobility is often among the primary objec- tives of such programs. Various approaches have been used to assess prosthetic mobility. They include performance tests, 6,7 categories of ambulation, 8-11 self-reported capability, and pros- thetic use over a variety of ambulation activities. 12-17 The optimal approach to assessment would be to use a combination of objective and subjective assessments to capture the many dimensions and qualities that contribute to a rehabilitation outcome. However, when faced with a busy clinical practice, using a battery of assessments to capture all the various dimen- sions is often not feasible. There are strengths and limitations associated with each approach. One advantage of self-report measures appealing to both research and clinical applications, especially in clinics responsible for large geographic regions, is that assessment of prosthetic mobility can occur by mail or telephone. One criticism of outcome measures for the amputee population is that many instruments have no known published psychometric properties. Three self-report scales of prosthetic mobility for the ampu- tee population have recently received attention in the literature. These include the Houghton Scale, the Prosthesis Evaluation Questionnaire (PEQ), and the Prosthetic Profile of the Amputee Locomotor Capabilities Index (PPA-LCI). The authors of the PPA-LCI and the PEQ have reported psychometric proper- ties. 12,17 The Houghton Scale, however, has face validity but no known published psychometric information is available. 12,17 Comparative psychometric information makes the task of se- lecting a scale easier. However, interpreting psychometric in- From the Faculty of Medicine, School of Rehabilitation Sciences, University of British Columbia, Vancouver, BC (Miller); and Departments of Physical Medicine and Rehabilitation (Deathe) and Epidemiology and Biostatistics (Speechley), Univer- sity of Western Ontario, London, Ont, Canada. Accepted in revised form November 20, 2000. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated. Reprint requests to William Miller, PhD, Faculty of Medicine, Schl of Rehabili- tation Sciences, T325-2211 Wesbrook Mall, University of British Columbia, Van- couver, BC V6T 2B5, Canada, e-mail: bcmiller@telus.net. 0003-9993/01/8210-6257$35.00/0 doi:10.1053/apmr.2001.25987 1432 Arch Phys Med Rehabil Vol 82, October 2001