Clinical Interpretation of Computerized Adaptive Test–Generated Outcome Measures in Patients With Knee Impairments

Abstract 

Wang Y-C, Hart DL, Stratford PW, Mioduski JE. Clinical interpretation of computerized adaptive test–generated outcome measures in patients with knee impairments.

Objective

To describe meaningful interpretations of functional status (FS) outcomes measures estimated using a body-part specific computerized adaptive test (CAT).

Design

A prospective observational cohort study.

Setting

Outpatient physical therapy clinics (291 clinics) in 30 U.S. states.

Participants

Sample of 21,896 patients with knee impairments receiving outpatient physical therapy.

Interventions

Not applicable.

Main Outcome Measure

FS estimated using CAT administration.

Results

We investigated 4 approaches to clinically meaningful interpretations of outcomes data: (1) 95% confidence interval for each score estimate, (2) percentile rank of FS scores, (3) responsiveness, and (4) functional staging. Overall, precision of a single score was estimated by FS score ±5. Based on score distribution, percentile ranks at 25th, 50th, and 75th percentiles corresponded to intake FS scores of 33, 42, and 51 and discharge FS scores of 51, 61, and 74, respectively. Results showed that 9 or higher FS change units represented statistically and clinically important improvement. Patients were classified into 6 hierarchical levels of FS using functional staging.

Conclusions

Results suggest how CAT-generated outcomes measures can be interpreted to assist clinicians and patients during rehabilitation.

Key Word: Rehabilitation

List of Abbreviations: CAT, computerized adaptive test, CI, confidence interval, FS, functional status, GROC, Global Rating of Change, IRT, item response theory, LEFS, Lower Extremity Functional Scale, MCII, minimal clinically important improvement, MDC₉₀, 90% confidence interval of the minimal detectable change, MDC₉₅, 95% confidence interval of the minimal detectable change, PRO, patient-reported outcome, RCI, reliable change index, ROC, receiver operating characteristic, RSM, Rating Scale Model