ABSTRACT
PURPOSE: To develop a valid measure of lower limb amputee mobility suitable for routine clinical use, including monitoring change. METHODS: The Special Interest Group in Amputee Medicine (SIGAM) described a single-item scale comprising six clinical grades (A-F) of amputee mobility. A self-report questionnaire was developed and algorithm designed to facilitate grade assignment. Reproducibility of the questionnaire and grades were assessed in 62 amputees. Concurrent validity and sensitivity to change were investigated using the timed walking test (TWT). The mobility construct was examined in 200 amputees, using item response theory, by co-calibration with the Rivermead Mobility Index (RMI) on the same patients. RESULTS: Patients included 144 males and 66 females, aged 13-90. Intraclass correlation coefficients and reproducibility kappa values were satisfactory. Observers agreed 100% in using the algorithm. TWT improved as SIGAM grade increased. Examination of psychometric properties revealed the SIGAM item fitted within the RMI mobility matrix. Average measures for the six grades were ordered correctly. There was no local dependency or differential item functioning for clinically relevant patient subgroups. The SIGAM scale showed an effect size of 10.66. CONCLUSIONS: The SIGAM mobility grades represent a novel, valid, clinically useful measure of amputee mobility which is also sensitive to change.
Subject(s)
Activities of Daily Living , Algorithms , Amputation, Surgical/rehabilitation , Health Status Indicators , Walking , Adolescent , Adult , Aged , Amputation, Surgical/methods , Artificial Limbs , Disability Evaluation , Female , Humans , Lower Extremity , Male , Middle Aged , Physical Therapy Modalities , Quality of Life , Sampling Studies , Sensitivity and Specificity , Severity of Illness Index , Surveys and Questionnaires , Treatment Outcome , United KingdomABSTRACT
PURPOSE: Measurement of lower limb amputee mobility was investigated using the Rivermead Mobility Index (RMI). METHOD: Reliability and reproducibility were assessed in 62 patients. The timed waking test (TWT) was used to investigate concurrent validity. The RMI construct was examined in 200 established amputees. RESULTS: One hundred and forty-four males and 66 females, aged 13-90 were recruited. Intraclass correlation coefficients and kappa statistics showed good reproducibility. Spearman correlation coefficient between the RMI and TWT -0.58 (p<0.000). Psychometric properties of the RMI were tested using item response theory. Hierachical differences in RMI grades were identified in amputees compared with neurologically impaired patients for which the RMI was developed. The RMI construct was not unidimensional, with redundancy of items and local dependency. At the upper end of the scale there were insufficient items measuring high levels of mobility. Finally, differential item functioning showed items behaving differently for patient subgroups. CONCLUSIONS: Although initial impressions suggest the RMI is a useful measure of lower limb amputee mobility, further analysis shows it is not appropriate for all amputees, with a number of limitations of its psychometric properties. Its use is not recommended in this population.
