Interrater and intrarater reliability of common clinical standing balance tests for people with hip osteoarthritis.

BACKGROUND Hip osteoarthritis (OA) is a common musculoskeletal condition affecting older individuals. Clinical balance tests are frequently used to assess standing balance in these people. There is insufficient information regarding the reliability of these tests. OBJECTIVE The aim of this study was to estimate reliability and measurement error of 4 common clinical standing balance tests in people with hip OA. DESIGN A prospective study was conducted with repeated measures between 2 independent raters within 1 session and within 1 rater over a 1-week interval. METHODS Thirty people with hip OA were evaluated. Reliability was estimated for the Four-Square Step Test, Step Test, Functional Reach Test, and Timed Single-Leg Stance Test using intraclass correlation coefficients (ICC [2,1]). Measurement error was expressed as standard error of measurement and minimal detectable change. RESULTS The Four-Square Step Test, Step Test, and Timed Single-Leg Stance Test were sufficiently reliable between raters (ICC=.85-.94, lower 1-sided 95% confidence interval [95% CI]=.71-.89), whereas the Step Test (standing on study limb) and Timed Single-Leg Stance Test (standing on nonstudy limb) were sufficiently reliable within a rater over a 1-week interval (ICC=.91, lower 1-sided 95% CI=.80-.83). The Step Test (standing on study limb) and Timed Single-Leg Stance Test (standing on nonstudy limb) achieved optimal levels of reliability (ICC >.90, lower 1-sided 95% CI >.70), with acceptable measurement error (<10%) for clinical outcome measures. The Functional Reach Test was not sufficiently reliable. A ceiling effect was detected for the Timed Single-Leg Stance Test. LIMITATIONS Reliability was assessed only between 2 raters during a single session and within 1 rater over a 1-week interval, which limits generalizability. CONCLUSIONS The Step Test (standing on study limb) is recommended as a highly reliable test with acceptable measurement error for assessing standing balance in people with hip OA.