Test-Retest Reliability of an Abbreviated Self-Report Overall Health Status Measure

Abstract
Test-retest reliability study. To assess test-retest reliability and estimate minimal detectable change of an overall measure and 2 summary measures of patient self-report of health status. Change in patient self-report of health status is a common outcome measure following rehabilitation. Because collection of health status data takes time and clinicians are required to be productive, selected items from reliable instruments were used to form a new, abbreviated instrument of health status relevant to patients in outpatient rehabilitation. There are no test-retest reliability statistics of these health status measures in this population. A convenience sample of 71 patients (mean age +/- SD, 41.9 +/- 17.9 years; age range, 15-83 years; sex, 35% male), with a variety of orthopaedic diagnoses, seeking rehabilitation in 2 outpatient facilities, volunteered. Patients completed health status questionnaires at initial evaluation and at 24 to 72 hours following evaluation. Intraclass correlation coefficients (ICC2.1) were used to estimate test-retest reliability and to estimate measurement error and minimal detectable changes. ICCs with a 1-sided lower limit 95% confidence intervals (CI) of the Overall Health Status measure and the Physical and Mental Component Summary measures for patients with chronic symptoms were 0.92 (0.85), 0.82 (0.68), and 0.85 (0.74), respectively. Minimal detectable changes (90% CI) were +/-12 (scale range, 100), +/- 9 (scale range, 60), and +/- 9 (scale range, 60) scale points, respectively, for the same measures. Results support the test-retest reliability of the Overall Health Status measure and summary measures for patients with chronic symptoms and demonstrate ability of the Overall Health Status and Physical Summary Scale measures to detect improvement of patient self-report of health status within the first few days of rehabilitation.

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