Table 2. Comparisons Between Constant-Load and Graded
Treadmill Protocols
|
Constant |
Graded |
|
| Variability |
| ICD
(within-subject) |
40% |
20% |
| ACD
(within-subject) |
30% |
12% |
| ACD
(between-subjects) |
60% |
30% |
| Placebo response |
| ICD |
36% |
0% |
| ACD |
25% |
0% |
| Dynamic
range |
Limited |
Large |
| Entry
exclusions |
20% |
0% |
| Exit exclusions |
45% |
0% |
| Equipment |
Basic |
Complex |
| Patient
acceptance |
Good |
Good |
| No. of
patients per group 25% change |
98 |
22 |
|
Estimates of treadmill variability (expressed as the coefficient
of variation) and placebo response were taken from published reports of
the different treadmill testing methodologies,16 20
including a direct comparison between the constant and graded
protocols.22 ACD is the absolute (maximal) claudication
distance and ICD is the initial claudication distance. The estimated
number of entry and exit exclusions (percent of patients no longer
limited by claudication within dynamic range of test) were taken from
published reports.12 23 24 The estimates
of sample size
were based on a two-tailed test, P<.05, and power of .80
for detecting a 25% difference between treated and control subjects,
based on published data.10 23
