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Lower extremity prosthetic mobility: a comparison of 3 self-report scales.

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 analyses, 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 confidence, and other indicators of ambulatory ability.


RESULTS
The reliability of the PPA-LCI (intraclass correlation 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. Evidence 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 hypothesized in all the scales. Each of the scales was able to discriminate between different groups for amputation cause, walking distance, mobility device use, and automatism, with each having varying strength related to relative precision. The Houghton Scale was the only scale able to distinguish between amputation 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.