title: Simulated computerized adaptive tests for measuring functional status were efficient with good discriminant validity in patients with hip, knee, or foot/ankle impairments.
abstract: OBJECTIVE
  To develop computerized adaptive tests (CATs) designed to assess lower extremity functional status (FS) in people with lower extremity impairments using items from the Lower Extremity Functional Scale and compare discriminant validity of FS measures generated using all items analyzed with a rating scale Item Response Theory model (theta(IRT)) and measures generated using the simulated CATs (theta(CAT)).
  
  
  METHODS
  Secondary analysis of retrospective intake rehabilitation data.
  
  
  RESULTS
  Unidimensionality of items was strong, and local independence of items was adequate. Differential item functioning (DIF) affected item calibration related to body part, that is, hip, knee, or foot/ankle, but DIF did not affect item calibration for symptom acuity, gender, age, or surgical history. Therefore, patients were separated into three body part specific groups. The rating scale model fit all three data sets well. Three body part specific CATs were developed: each was 70% more efficient than using all LEFS items to estimate FS measures. theta(IRT) and theta(CAT) measures discriminated patients by symptom acuity, age, and surgical history in similar ways. theta(CAT) measures were as precise as theta(IRT) measures.
  
  
  CONCLUSIONS
  Body part-specific simulated CATs were efficient and produced precise measures of FS with good discriminant validity.
authors.affiliation: Focus On Therapeutic Outcomes, Inc., White Stone, VA 22578-2403, USA. dsailhart@rivnet.net
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Hart
authors.forename: Jerome E
authors.initials: JE
authors.lastname: Mioduski
authors.forename: Paul W
authors.initials: PW
authors.lastname: Stratford
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000843:Ankle Joint / Q000503:physiopathology; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006305:Health Status Indicators; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D007592:Joint Diseases / Q000503:physiopathology / Q000534:rehabilitation*; D007719:Knee Joint / Q000503:physiopathology; D035002:Lower Extremity / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies