Computerized adaptive test for patients with foot or ankle impairments produced valid and responsive measures of function.
OBJECTIVE
We tested the item response theory (IRT) model assumptions of the original item bank, and evaluated the practical and psychometric adequacy, of a computerized adaptive test (CAT) for patients with foot or ankle impairments seeking rehabilitation in outpatient therapy clinics.


METHODS
Data from 10,287 patients with foot or ankle impairments receiving outpatient physical therapy were analyzed. We first examined the unidimensionality, fit, and invariance IRT assumptions of the CAT item bank. Then we evaluated the efficiency of the CAT administration and construct validity and sensitivity of change of the foot/ankle CAT measure of lower-extremity functional status (FS).


RESULTS
Results supported unidimensionality, model fit, and invariance of item parameters and patient ability estimates. On average, the CAT used seven items to produce precise estimates of FS that adequately covered the content range with negligible floor and ceiling effects. Patients who were older, had more chronic symptoms, had more surgeries, had more comorbidities, and did not exercise prior to receiving rehabilitation reported worse discharge FS. Seventy-one percent of patients obtained statistically significant change at follow-up. Change of 8 FS units (scale 0-100) represented minimal clinically important improvement.


CONCLUSIONS
We concluded that the foot/ankle item bank met IRT assumptions and that the CAT FS measure was precise, valid, and responsive, supporting its use in routine clinical application.
Hart
Dennis L
DL
Focus on Therapeutic Outcomes, Inc., 551 Yopps Cove Road, White Stone, VA, 22578-2403, USA. hart@fotoinc.com
Wang
Ying-Chih
YC
Stratford
Paul W
PW
Mioduski
Jerome E
JE
D000223:Adaptation, Psychological; D000293:Adolescent; D000328:Adult; D000368:Aged; D016512:Ankle Injuries / Q000523:psychology* / Q000534:rehabilitation; D003201:Computers; D004185:Disability Evaluation; D005260:Female; D018409:Foot Injuries / Q000523:psychology* / Q000534:rehabilitation; D006801:Humans; D035002:Lower Extremity / Q000473:pathology; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D010045:Outpatients; D010865:Pilot Projects; D011594:Psychometrics; D011788:Quality of Life / Q000523:psychology*; D012372:ROC Curve; D012984:Software; D055815:Young Adult