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A study of the inter-rater reliability of a test battery for use in patients after total hip replacement
Lone Ramer Mikkelsen1, Søren Mikkelsen2, Kjeld Søballe3
1Interdisciplinary Research Unit, Silkeborg Regional Hospital, Silkeborg, Denmark lonemike@rm.dk.
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).
