The reliability and validity of the L-test in people with Parkinson’s disease

Abstract

Objective To evaluate the test–retest and concurrent validity of the L-test in a group of participants with mild to moderate Parkinson’s disease. The L-test is an extended version of the Timed up and Go test, incorporating a longer walking distance and turns in two directions.

Design Cross-sectional.

Setting Community.

Participants 16 participants (13 male), mean age 75 (SD 6.7) mean duration since diagnosis 7.1 years (±2.8). Disease severity was mild to moderate on the Hoehn and Yahr scale (mean 2.1; mode 2; range 1–3). 14 participants (12 male) completed the study.

Interventions Not applicable.

Main outcome measures A Bland and Altman plot examined the agreement between first and second testing occasion of the L-test. Intra-class correlation coefficients (ICC) assessed the test–retest reliability. Concurrent validity was established by correlating the L-test with the Timed up and Go test (TUG). The Minimal Detectable Change with 95% confidence interval (MDC95) was calculated to determine the true change not due to chance.

Results The L-test showed excellent test–retest reliability on the Bland & Altman plot and the ICC. There was a high degree of agreement between measurements taken on days 1 and 2. The L-test correlated strongly with the Timed up and Go test on both measurement days with r = 0.97 (p < 0.001) and r = 0.96 (p < 0.001). The MDC95 was 5.31 seconds.

Conclusions The L-test is a reliable and valid outcome measurement for the assessment of walking ability in participants with mild to moderate Parkinson’s disease.