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The Foot Function Index with Verbal Rating Scales (FFI-5pt): A Clinimetric Evaluation and Comparison with the Original FFI
MARIJKE M. KUYVENHOVEN, KEES J. GORTER, PETER ZUITHOFF, ELLY BUDIMAN-MAK, KENDON J. CONRAD, and MARCEL W.M. POST
ABSTRACT.
Methods. A prospective study was performed on 206 patients with nontraumatic forefoot complaints. Scoring, internal consistency, and construct validity of the FFI-5pt were compared with those of the original FFI, which rates all items on VAS. We also studied agreement between the scores at baseline and after one and 8 weeks and the scale scores with regard to sex, age, presence of osteoarthritis, limitation of mobility, bodily pain, and poor physical functioning (using SF-36). Results. Some items were not applicable; removal of these items left 2 scales (Pain and Disability) with high internal consistency (a = 0.88 to 0.94) and good agreement between both versions (intraclass correlation coefficient 0.64 to 0.79). Principal component analysis with varimax rotation using a forced 2 factor model fitted well (65% explained variance). Test-retest reliability was high (ICC 0.70 to 0.83), while the stability over 8 weeks was lower, but still good (ICC 0.63 to 0.71). Responsiveness to change was low to moderate. However, a small number of patients reported an overall change (19%). Scores of patients with limited mobility and poor physical health (SF-36) were higher than those of patients with fewer physical problems, indicating good concurrent validity. Conclusion. The FFI-5pt is a suitable generic measure. Its clinimetric properties are comparable with those of the original FFI. Its administration and data entry are less time consuming. However, responsiveness has to be more exactly assessed in an intervention study. (J Rheumatol 2002;29:1023-8) Key Indexing Terms:
FOOT
From the Julius Center for General Practice and Patient Oriented Research, University Medical Center (UMC) Utrecht, Utrecht, The Netherlands; Midwest Center for Health Services and Policy Research, VA Hospital, Hines, Illinois; Loyola University, Chicago, and Strich School of Medicine, Maywood, Illinois; School of Public Health, University of Chicago, Chicago, Illinois, USA; and the Institute for Rehabilitation Research, Hoensbroek, The Netherlands. Supported by grant 97-2-204 from the Dutch League against Rheumatism. M.M. Kuyvenhoven, PhD, Senior Lecturer, Medical Sociologist; K.J. Gorter, MD, General Practitioner; P. Zuithof, MSc, Psychologist, Julius Center for General Practice and Patient Oriented Research, University Medical Center Utrecht; E. Budiman-Mak, MD, MS, MPH, Associate Professor, Research Consultant, Midwest Center for Health Services and Policy Research and Strich School of Medicine; K.J. Conrad, PhD, Professor, Research Scientist, Midwest Center for Health Services and Policy Research, School of Public Health, University of Chicago; M.W.M. Post, PhD, Psychologist, Institute for Rehabilitation Research. Address reprint requests to Dr. M.M. Kuyvenhoven, Julius Center for General Practice and Patient Oriented Research, University Medical Center (UMC) Utrecht, PO Box 85060, 3508 AB Utrecht, The Netherlands. E-mail: m.m.kuyvenhoven@med.uu.nl Submitted July 26, 2001; revision accepted November 29, 2001. |