Clinical Interpretation of Computerized Adaptive Test Outcome Measures in Patients With Foot/Ankle Impairments

STUDY DESIGN: Prospective cohort study of 10 287 patients with foot/ankle impairments receiving outpatient physical therapy. OBJECTIVES: To describe meaningful interpretations of functional status (FS) outcomes measures, estimated using a body-part-specific computerized adaptive test (CAT). BACKGROUND: Increased use of CATs to generate outcome measures in rehabilitation has stimulated questions concerning score interpretation. Identifying meaningful intra-individual change and reporting clinical interpretation of those generated outcomes are essential to advance the quality of rehabilitation practice. METHODS: We performed 4 approaches to clinically interpret outcomes data. First, we used the standard error of the estimate to construct a 90% confidence interval for each CAT estimated score. Second, we presented the percentile rank of FS scores. Third, we used 2 threshold approaches to define individual-patient-level change: statistically reliable change and clinically important change. Last, we illustrated a functional staging method. RESULTS: Precision of a single score was estimated by an FS score of +/- 4. Based on score distribution, percentile ranks at 25th, 50th, and 75th percentiles corresponded to intake FS scores of 38, 47 and 57 and discharge FS scores of 52, 64, and 77, respectively. Minimal detectable change supported 7 or more FS change units out of 100 represented statistically reliable change, and ROC analyses supported 8 or more FS change units represented minimal clinically important improvement. Using a functional staging system, we established 5 hierarchical functional status levels. CONCLUSION: CAT-generated outcome measures can be interpreted to improve clinical interpretation and to assist clinicians in using patient-reported outcomes during therapy practice. J Orthop Sports Phys Ther 2009;39(10):753-764. doi:10.2519/jospt.2009.3122