Measuring Activity Limitations in Walking: Development of a Hierarchical Scale for Patients With Lower-Extremity Disorders Who Live at Home

Roorda LD, Roebroeck ME, van Tilburg T, Molenaar IW, Lankhorst GJ, Bouter LM, and the Measuring Mobility Study Group. Measuring activity limitations in walking: development of a hierarchical scale for patients with lower-extremity disorders who live at home. To develop a hierarchical scale that measures activity limitations in walking in patients with lower-extremity disorders who live at home. Cross-sectional study. Orthopedic workshops and outpatient clinics of secondary and tertiary care centers. Patients (N=981; mean age ± standard deviation, 58.6±15.4y; 46% men) living at home, with different lower-extremity disorders: stroke, poliomyelitis, osteoarthritis, amputation, complex regional pain syndrome type I, and diabetic and degenerative foot disorders. Not applicable. (1) Fit of the monotone homogeneity model, indicating whether items can be used for measuring patients; (2) fit of the double monotonicity model, indicating invariant (hierarchical) item ordering; (3) intratest reliability, indicating repeatability of the sum score; (4) robustness, addressing the clinimetric properties within subgroups of patients; and (5) differential item functioning, addressing the validity of comparisons between subgroups of patients. Thirty-five of 41 dichotomous items had (1) good fit of the monotone homogeneity model (coefficient H=.50), (2) good fit of the double monotonicity model (coefficient H T =.33), (3) good intratest reliability (coefficient ρ=.95), (4) satisfactory robustness (within subgroups of patients defined by age, sex, and diagnosis), and (5) some differential item functioning (6 items in amputees compared with nonamputees). A hierarchical scale, with excellent scaling characteristics, was developed to measure activity limitations in walking in patients with lower-extremity disorders who live at home. The measurements should be interpreted cautiously when making comparisons between amputees and nonamputees.