Objective: To assess the within-day inter-rater reliability of a test battery of functional performance, muscle strength and leg extension power on total hip replacement patients.
Design: A test-retest design was used.
Setting: Orthopaedic department at a Regional Hospital in Denmark.
Subjects: Two convenience samples of 20 total hip replacement patients were included.
Intervention: The tests were performed three months after total hip replacement. Two raters performed test and re-test, with two hours rest in-between.
Main measures: The test battery included: sit-to-stand performance, 20-metre maximum walking speed, stair climb performance, isometric muscle strength (hip abduction/flexion), and leg extension power. Absolute reliability was assessed with Bland Altman plots, standard error of measurement (SEM), and minimal detectable change. Relative reliability was assessed with intra-class correlation coefficient.
Results: Systematic differences between testers were seen in tests of walking speed (0.32 seconds p = 0.03) and stair climb performance (0.18 seconds p = 0.003). In per cent of the grand mean, the standard error of measurement was 3%-10%, indicating the measurement error on a group level, and the minimal detectable change was 10%-27%, indicating the measurement error on an individual level. The intra-class correlation coefficients were above 0.80 in all tests (range 0.83-0.95).
Conclusions: The tests showed acceptable relative and absolute inter-rater reliability on a group level, but not on an individual level (except from test of walking speed and stair climb performance). Systematic differences between testers were considered clinically irrelevant (0.3 and 0.2 seconds).
Keywords: Arthroplasty; measurement error; muscle strength; reliability; walking.
© The Author(s) 2014.