A Computerized Adaptive Test for Patients With Hip Impairments Produced Valid and Responsive Measures of Function

Abstract 

Hart DL, Wang Y-C, Stratford PW, Mioduski JE. A computerized adaptive test for patients with hip impairments produced valid and responsive measures of function.

Objectives

To describe the use of a computerized adaptive test (CAT) in routine clinical practice and evaluate content coverage and construct validity, sensitivity to change, and responsiveness of hip CAT functional status (FS) measures.

Design

Longitudinal, prospective observational cohort study.

Setting

Two hundred fifty-seven outpatient rehabilitation clinics in 31 states (United States).

Participants

Two samples were examined: intake and discharge rehabilitation FS data from patients (N=8714) treated for hip impairments between January 2005 and June 2007 and data from patients (N=444) used to develop the hip CAT were examined for comparison (2002–2004).

Interventions

Not applicable.

Main Outcome Measures

Hip functional status and global rating of change.

Results

The CAT used on average 7 items to produce precise estimates of FS that adequately covered the content range with negligible floor and slight ceiling effects. Test information functions and SEs supported FS measure precision. FS measures discriminated patients in clinically logical ways. Sixty-one percent of patients obtained discharge FS measures greater than or equal to minimal detectable change (95% confidence intervals). Change of 6 FS units (scale: 0–100) represented minimal clinically important improvement, which 64% of patients obtained.

Conclusions

The hip CAT was efficient; produced valid, responsive measures of FS for patients receiving therapy for hip impairments; and functioned well in routine clinical application but would benefit from more difficult items.

Key Word: Rehabilitation

List of Abbreviations: CAT, computerized adaptive test, CI, confidence interval, DIF, differential item functioning, FCI, Functional Comorbidity Index, FOTO, Focus On Therapeutic Outcomes, Inc., FS, functional status, GROC, global rating of change, IER, item exposure rate, LEFS, Lower Extremity Functional Scale, MCII, minimal clinically important improvement, MDC, minimal detectable change, MDC₉₀, minimal detectable change at the 90% CI, MDC₉₅, minimal detectable change at the 95% CI, PRO, patient-reported outcome, ROC, receiver operating characteristic analyses