Validity and reliability of 2-min step test in patients with symptomatic peripheral artery disease

Background: Although 2-min step test (2MST) has been useful in general population, no study has investigated its validity in patients with peripheral artery disease (PAD).

Objective: To analyze the validity and reliability of the 2MST in patients with PAD and claudication symptoms.

Methods: Twenty-four patients with PAD and claudication symptoms were recruited and performed the 2MST comparing it to the six-minute walk test (6MWT). Test performance, step indicators, and heart rate were measured during the test. Validity was verified using Pearson correlation between the performance of 2MST (number of steps) and 6MWT (distance and number of steps). The reliability was analyzed by the intraclass correlation coefficient and by the limits of agreement of Bland and Altman.

Results: A similar performance was observed between the two 2MST (65 ± 10 steps vs. 66 ± 10 steps, p = 0.43) with a significant intraclass coefficient correlation of 0.945. The bias between tests was of 0.79 steps with the limits of agreement between -9.6 and 11.2 steps. The 90% minimum detectable difference was 3.2 steps. The number of steps in 2MST was significantly correlated with the number of steps in 6MWT (r = 0.55, p<0.01). However, the number of steps in 2MST did not correlate with distance in the 6MWT (r = 0.26, p = 0.23). The peak heart rate was lower in 2MST compared to 6MWT (p<0.05).

Conclusion: The 2MST present adequate reliability and validity in patients with symptomatic PAD.