Treadmill testing for evaluation of claudication: Comparison of constant-load and graded-exercise tests

Objectives: To compare the correlation and practicability of single-stage vs. graded treadmill protocols in the assessment of the absolute claudication distance (ACD). Design: Randomized open study. Material and methods: In 52 patients with peripheral arterial occlusive disease, the ACD on treadmill at 3km/h and 12% grade (constant-load test = C-test) ranged from 50 to 400m. The C-test and the graded-exercise test (walking on the treadmill at 3km/h and 0% gradient for 3 min, with subsequent increase in gradient of 3.5% every 3 min = G-test) were carried out at random on the same clay under standardized conditions. Results: The ACD was higher in the G-test than in the C-test (360.4+/-208.8m vs. 166.5+/-93.6m; p<0.001). The coefficients of variation were very similar (57.9% and 56.2%, respectively). In the subgroup of patients with an ACD between 100m and 150m, a large difference was found both for the coefficient of variation (58.6% G-test, 9.6% C-test) and for the standard deviation (339.8+/-199.0m and 133.1+/-12.8m, respectively). Conclusions: For the assessment of the ACD in patients with severe claudication the C-test would seem to be more suitable than the G-test.