The test-retest reliability, concurrent validity, and minimal detectable change of the L test in patients with total hip arthroplasty

BACKGROUND: The L test is a modified version of the timed up and go test (TUG) with an L-shaped walking path. The L test is more extensive than other performance tests, especially in turn direction and specific tasks. The study aimed to evaluate the test-retest reliability, concurrent validity, and minimal detectable change of the L test in patients with total hip arthroplasty (THA). A cross-sectional study was conducted with 33 unilateral and primary THA patients. The L test was performed twice with an interval of an hour on the same day for the test-retest reliability. Timed up and go test (TUG), five times sit to stand test (FTST), and Harris hip score (HHS) were carried out for the analysis of the concurrent validity of the L test. RESULTS: The mean age of the participants was 74.6 ± 10.3 years. The ICC score of the L test was 0.992. Test-retest reliability was excellent. SEM(95) and MDC(95) values were 3.39 and 9.39, respectively. Both TUG and HHS were strongly correlated with the L test (r(1) = 0.889, r(2) = −0.568, p < 0.001). However, there was no significant correlation between FTST and L test (r = 0.024, p > 0.05). CONCLUSIONS: The L test is valid and reliable performance measurement in patients with primary unilateral THA. MDC(95) of the L test is an essential reference for clinicians in the rehabilitation follow-up process of THA patients.